summaryrefslogtreecommitdiffstats
path: root/drivers/spi/spi_imx.c
AgeCommit message (Collapse)Author
2010-01-20spi/spi_imx: add device information by switching pr_debug() to dev_dbg()Alberto Panizzo
Useful when debugging multiple spi channels. Signed-off-by: Alberto Panizzo <maramaopercheseimorto@gmail.com> Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
2009-12-13spi: fix probe/remove section markingsGrant Likely
Probe/remove functions need to be marked as __devinit and __devexit (not __init an __exit) to prevent trying to run code that has been discarded. This patch fixes the spi_imx driver to mark probe and remove correctly. Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
2009-12-13spi-imx: don't access struct device directly but use dev_get_platdataUwe Kleine-König
Also there is no casting needed to assign a void pointer. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
2009-12-13spi-imx: Add mx25 supportSascha Hauer
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
2009-12-13spi-imx: use positive logic to distinguish cpu variantsUwe Kleine-König
This is much safer when support for new variants is added. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
2009-12-13spi-imx: correct check for platform_get_irq failingUwe Kleine-König
platform_get_irq returns -ENXIO if there is no entry. So ensure return value is greater than zero instead of non-zero. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
2009-12-08spi/i.MX: fix broken error handling for gpio_requestJohn Ogness
i.MX35-provided chipselects are represented using negative numbers. If gpio_request() fails and the previous chipselect was a negative number, the while loop is endless (i is never decremented). Also, the error loop would never call gpio_free on chipselect[0]. And finally, the error message was missing an endline. Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
2009-12-08spi/i.mx: drain MXC SPI transfer buffer when probing deviceDaniel Mack
On the MX31litekit, the bootloader seems to communicate with the MC13783 PMIC chip before booting Linux. However, it does not flush all the buffers properly after that, which makes the imx-spi driver read bogus data when probing the MC13783. Fix that by draining the SPI receive buffer on startup. Signed-off-by: Daniel Mack <daniel@caiaq.de> Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
2009-10-01spi-imx: strip down chipselect function to only drive the chipselectUwe Kleine-König
spi_imx_chipselect() made things that should be (and mostly are) done by spi_imx_setupxfer. Only setting the tx and rx functions was missing. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Acked-by: Sascha Hauer <s.hauer@pengutronix.de> Cc: David Brownell <dbrownell@users.sourceforge.net> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-10-01spi-imx: initialize complete config structUwe Kleine-König
Otherwise the config function uses random data from the stack. This didn't stick out because config is called once more in the chipselect function with correct parameters. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Acked-by: Sascha Hauer <s.hauer@pengutronix.de> Cc: David Brownell <dbrownell@users.sourceforge.net> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-10-01spi-imx: no need to assert bits_per_word being initializedUwe Kleine-König
spi_imx_setup() is only called by spi_setup(). The latter does the initialization already. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Acked-by: Sascha Hauer <s.hauer@pengutronix.de> Cc: David Brownell <dbrownell@users.sourceforge.net> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-10-01spi-imx: setup mode_bits we can handleSascha Hauer
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Cc: David Brownell <dbrownell@users.sourceforge.net> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-10-01spi-imx: fix initial chipselect settingsSascha Hauer
We can only setup the gpio pins in spi_setup time when we know the SPI_CS_HIGH setting. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Cc: David Brownell <dbrownell@users.sourceforge.net> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-10-01spi-imx: update state correctlySascha Hauer
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Cc: David Brownell <dbrownell@users.sourceforge.net> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-10-01spi-imx: rename source file to spi_imx.cUwe Kleine-König
This makes the filename match the Kconfig symbol and the driver name. Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Cc: Sascha Hauer <s.hauer@pengutronix.de> Cc: David Brownell <dbrownell@users.sourceforge.net> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-09-23spi: remove i.MX SPI driverSascha Hauer
This driver is in a non working state at the moment and will be replaced by a bitbang driver which can also handle the newer i.MX variants Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de> Acked-by: David Brownell <david-b@pacbell.net> Acked-by: Andrea Paterniani <a.paterniani@swapp-eng.it> Cc: Russell King <rmk@arm.linux.org.uk> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-18spi: move more spi_setup() functionality into coreDavid Brownell
Move some common spi_setup() error checks into the SPI framework from the spi_master controller drivers: - Add a new "mode_bits" field to spi_master - Use that in spi_setup to validate the spi->mode value being requested. Setting this new field is now mandatory for any controller supporting more than vanilla SPI_MODE_0. - Update all spi_master drivers to: * Initialize that field * Remove current spi_setup() checks using that value. This is a net minor code shrink. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-18spi: move common spi_setup() functionality into coreDavid Brownell
Start moving some spi_setup() functionality into the SPI core from the various spi_master controller drivers: - Make that function stop being an inline; - Move two common idioms from drivers into that new function: * Default bits_per_word to 8 if that field isn't set * Issue a standardized dev_dbg() message This is a net minor source code shrink, and supports enhancments found in some follow-up patches. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-07spi_imx: set spi_master.dma_alignment = 4Mike Rapoport
Signed-off-by: Mike Rapoport <mike@compulab.co.il> Cc: Bryan Wu <bryan.wu@analog.com> Cc: David Brownell <david-b@pacbell.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-04-07spi: limit reaches -1, tested 0Roel Kluin
With a postfix decrement limit will reach -1 rather than 0, so the warning will not be issued. Also, add a cpu_relax() into the busy-wait loop. Signed-off-by: Roel Kluin <roel.kluin@gmail.com> Cc: Mariusz Ceier <mceier@gmail.com> Acked-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-03-24spi: struct device - replace bus_id with dev_name(), dev_set_name()Kay Sievers
Cc: dbrownell@users.sourceforge.net Cc: spi-devel-general@lists.sourceforge.net Acked-by: Greg Kroah-Hartman <gregkh@suse.de> Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
2008-12-01spi: fix spi_imx probe oopsingJulien Boibessot
Corrects spi_imx driver oops during initialization/probing: can't use drv_data before it's allocated. Signed-off-by: Julien Boibessot <julien.boibessot@armadeus.com> Acked-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-11-19spi_imx: full duplex dma corruption bugfixAndrea Paterniani
Fix unsafe order in dma mapping operation: always flush data from the cache *BEFORE* invalidating it, to allow full duplex transfers where the same buffer may be used for both writes and reads. Signed-off-by: Andrea Paterniani <a.paterniani@swapp-eng.it> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-08-07[ARM] Move include/asm-arm/arch-* to arch/arm/*/include/machRussell King
This just leaves include/asm-arm/plat-* to deal with. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2008-08-07[ARM] Remove asm/hardware.h, use asm/arch/hardware.h insteadRussell King
Remove includes of asm/hardware.h in addition to asm/arch/hardware.h. Then, since asm/hardware.h only exists to include asm/arch/hardware.h, update everything to directly include asm/arch/hardware.h and remove asm/hardware.h. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2008-07-26dma-mapping: add the device argument to dma_mapping_error()FUJITA Tomonori
Add per-device dma_mapping_ops support for CONFIG_X86_64 as POWER architecture does: This enables us to cleanly fix the Calgary IOMMU issue that some devices are not behind the IOMMU (http://lkml.org/lkml/2008/5/8/423). I think that per-device dma_mapping_ops support would be also helpful for KVM people to support PCI passthrough but Andi thinks that this makes it difficult to support the PCI passthrough (see the above thread). So I CC'ed this to KVM camp. Comments are appreciated. A pointer to dma_mapping_ops to struct dev_archdata is added. If the pointer is non NULL, DMA operations in asm/dma-mapping.h use it. If it's NULL, the system-wide dma_ops pointer is used as before. If it's useful for KVM people, I plan to implement a mechanism to register a hook called when a new pci (or dma capable) device is created (it works with hot plugging). It enables IOMMUs to set up an appropriate dma_mapping_ops per device. The major obstacle is that dma_mapping_error doesn't take a pointer to the device unlike other DMA operations. So x86 can't have dma_mapping_ops per device. Note all the POWER IOMMUs use the same dma_mapping_error function so this is not a problem for POWER but x86 IOMMUs use different dma_mapping_error functions. The first patch adds the device argument to dma_mapping_error. The patch is trivial but large since it touches lots of drivers and dma-mapping.h in all the architecture. This patch: dma_mapping_error() doesn't take a pointer to the device unlike other DMA operations. So we can't have dma_mapping_ops per device. Note that POWER already has dma_mapping_ops per device but all the POWER IOMMUs use the same dma_mapping_error function. x86 IOMMUs use device argument. [akpm@linux-foundation.org: fix sge] [akpm@linux-foundation.org: fix svc_rdma] [akpm@linux-foundation.org: build fix] [akpm@linux-foundation.org: fix bnx2x] [akpm@linux-foundation.org: fix s2io] [akpm@linux-foundation.org: fix pasemi_mac] [akpm@linux-foundation.org: fix sdhci] [akpm@linux-foundation.org: build fix] [akpm@linux-foundation.org: fix sparc] [akpm@linux-foundation.org: fix ibmvscsi] Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> Cc: Muli Ben-Yehuda <muli@il.ibm.com> Cc: Andi Kleen <andi@firstfloor.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Avi Kivity <avi@qumranet.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-07-10Merge branch 'imx' into develRussell King
Conflicts: arch/arm/mm/Kconfig
2008-07-05IMX: introduce clock APISascha Hauer
This patch introduces the clock API for i.MX and converts all in-Kernel drivers to use it. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
2008-07-03[ARM] 5122/1: imx_dma_request_by_prio simpilficationPaulius Zaleckas
imx_dma_request_by_prio can return channel number by itself. No need to supply variable address through parameters. Also converted all drivers using this function. Signed-off-by: Paulius Zaleckas <paulius.zaleckas@teltonika.lt> Acked-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2008-04-28spi: spi_imx updatesAndrea Paterniani
Updates to the i.MX SPI controller driver: 1) Some comments changed and/or added. 2) End of transfers is now managed on TXFIFO empty interrupt after the last write to TXFIFO. This speeds interrupt execution by removing the wait for TXFIFO to become empty. On TXFIFO empty interrupt the handler needs only to poll for the end of the ongoing transaction (SPI_CONTROL_XCH) to close the transfer. (2.1) Write only transfers are closed flushing RXFIFO. (2.2) Read transfers are closed reading trailing bytes from RXFIFO. (2.3) Read transfers where RXFIFO overrun occurred are closed by flushing RXFIFO and aborting the message. 3) Fifos are now flushed via SPI disable after the end of ongoing transaction. Signed-off-by: Andrea Paterniani <a.paterniani@swapp-eng.it> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-04-11spi: fix platform driver hotplug/coldplugKay Sievers
Since 43cc71eed1250755986da4c0f9898f9a635cb3bf, the platform modalias is prefixed with "platform:". Add MODULE_ALIAS() to the hotpluggable SPI platform drivers, to allow module auto loading. [dbrownell@users.sourceforge.net: more drivers: registration fixes] Signed-off-by: Kay Sievers <kay.sievers@vrfy.org> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-06spi: remove more dev->power.power_state usageDavid Brownell
Remove some more references to dev->power.power_state. That field is overdue for removal, but we can't do that while it's still referenced in the kernel. The only reason to update it was to make the /sys/devices/.../power/state files (now removed) work better. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-03Spelling fixes: lenght->lengthPaulius Zaleckas
Signed-off-by: Paulius Zaleckas <pauliusz@yahoo.com> Signed-off-by: Adrian Bunk <bunk@kernel.org>
2007-12-10spi_imx: fix typo in descriptionWill Newton
Signed-off-by: Will Newton <will.newton@gmail.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-18Add missing newlines to some uses of dev_<level> messagesJoe Perches
Found these while looking at printk uses. Add missing newlines to dev_<level> uses Add missing KERN_<level> prefixes to multiline dev_<level>s Fixed a wierd->weird spelling typo Added a newline to a printk Signed-off-by: Joe Perches <joe@perches.com> Cc: "Luck, Tony" <tony.luck@intel.com> Cc: Jens Axboe <jens.axboe@oracle.com> Cc: Mark M. Hoffman <mhoffman@lightlink.com> Cc: Roland Dreier <rolandd@cisco.com> Cc: Tilman Schmidt <tilman@imap.cc> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Jeff Garzik <jeff@garzik.org> Cc: Stephen Hemminger <shemminger@linux-foundation.org> Cc: Greg KH <greg@kroah.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Geert Uytterhoeven <geert@linux-m68k.org> Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: David Brownell <david-b@pacbell.net> Cc: James Smart <James.Smart@Emulex.Com> Cc: Andrew Vasquez <andrew.vasquez@qlogic.com> Cc: "Antonino A. Daplas" <adaplas@pol.net> Cc: Evgeniy Polyakov <johnpol@2ka.mipt.ru> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Jaroslav Kysela <perex@suse.cz> Cc: Takashi Iwai <tiwai@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-16spi doesn't need class_deviceTony Jones
Make the SPI framework and drivers stop using class_device. Update docs accordingly ... highlighting just which sysfs paths should be "safe"/stable. Signed-off-by: Tony Jones <tonyj@suse.de> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: Greg KH <greg@kroah.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-10-16SPI driver runtime footprint shrinkageDavid Brownell
Shrink the runtime footprint of various SPI drivers: - Move the probe() routine into the init section where practical, using platform_driver_probe() to make that safe. This often saves around 1KB. Using platform_driver_probe() can also be a correctness fix, if the probe routine is already marked __init but the driver struct keeps a dangling pointer to it after init section removal. - Likewise move remove() routines into the exit sections. These changes would be inappropriate iff the platform devices were actually hotpluggable (e.g. they're found on optional addon cards, or in an FPGA that's dynamically reprogrammed). In these cases, that's not the situation; it's an SOC controller and the only device is initialized before these drivers. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-08-31SPI driver hotplug/coldplug fixesDavid Brownell
Update various SPI drivers so they properly support - coldplug through "modprobe $(cat /sys/devices/.../modalias)" - hotplug through "modprobe $(MODALIAS)" The basic rule for platform, SPI, and (new style) I2C drivers is just to make sure that modprobing the driver name works. In this case, all the relevant drivers are platform drivers, and this patch either (a) Changes the driver name, if no in-tree code would break; this is simpler and thus preferable in the long term. (b) Adds MODULE_ALIAS directives, when in-tree platforms declare devices using the current driver name; less desirable. Most systems will link SPI controller drivers statically, but there's no point in being needlessly broken. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Cc: Jean Delvare <khali@linux-fr.org> Acked-by: Andrei Konovalov <akonovalov@ru.mvista.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-17SPI controller drivers: check for unsupported modesDavid Brownell
Minor SPI controller driver updates: make the setup() methods reject spi->mode bits they don't support, by masking aginst the inverse of bits they *do* support. This insures against misbehavior later when new mode bits get added. Most controllers can't support SPI_LSB_FIRST; more handle SPI_CS_HIGH. Support for all four SPI clock/transfer modes is routine. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-06-01SPI: Freescale iMX SPI controller driver fixesAndrea Paterniani
Fix 2 bugs: - SPI_DMA_RHDMA bad value. - Missing return value in setup() function (lost passing from patch-2.6.20-rc4-spi_imx to patch-2.6.20-rc6-spi_imx). Signed-off-by: Andrea Paterniani <a.paterniani@swapp-eng.it> Cc: David Brownell <david-b@pacbell.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-20[PATCH] SPI controller build/warning fixesDavid Brownell
The signature of the per-device cleanup() routine changed to remove its const-ness. Three new SPI controller drivers now need that change, to eliminate build warnings. This also fixes a build bug with atmel_spi on AT91 systems. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-02-12[PATCH] SPI: Freescale iMX SPI controller driver (BIS+)Andrea Paterniani
Add the SPI controller driver for Freescale i.MX(S/L/1). Main features summary: > Per chip setup via board specific code and/or protocol driver. > Per transfer setup. > PIO transfers. > DMA transfers. > Managing of NULL tx / rx buffer for rd only / wr only transfers. This patch replace patch-2.6.20-rc4-spi_imx with the following changes: > Few cosmetic changes. > Function map_dma_buffers now return 0 for success and -1 for failure. > Solved a bug inside spi_imx_probe function (wrong error path). > Solved a bug inside setup function (bad undo setup for max_speed_hz). > For read-only transfers, always write zero bytes. This is almost the same as the 'BIS' version sent by Andrea, except for updating the 'DUMMY' byte so that read-only transfers shift out zeroes. That part of the API changed recently, since some half duplex peripheral chips require that semantic. Signed-off-by: Andrea Paterniani <a.paterniani@swapp-eng.it> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>