diff options
| -rw-r--r-- | Documentation/DocBook/uio-howto.tmpl | 40 | ||||
| -rw-r--r-- | drivers/uio/uio.c | 26 | ||||
| -rw-r--r-- | include/linux/uio_driver.h | 2 |
3 files changed, 67 insertions, 1 deletions
diff --git a/Documentation/DocBook/uio-howto.tmpl b/Documentation/DocBook/uio-howto.tmpl index fdd7f4f887b..c4d18731396 100644 --- a/Documentation/DocBook/uio-howto.tmpl +++ b/Documentation/DocBook/uio-howto.tmpl @@ -30,6 +30,12 @@ <revhistory> <revision> + <revnumber>0.5</revnumber> + <date>2008-05-22</date> + <authorinitials>hjk</authorinitials> + <revremark>Added description of write() function.</revremark> + </revision> + <revision> <revnumber>0.4</revnumber> <date>2007-11-26</date> <authorinitials>hjk</authorinitials> @@ -64,7 +70,7 @@ <?dbhtml filename="copyright.html"?> <title>Copyright and License</title> <para> - Copyright (c) 2006 by Hans-Jürgen Koch.</para> + Copyright (c) 2006-2008 by Hans-Jürgen Koch.</para> <para> This documentation is Free Software licensed under the terms of the GPL version 2. @@ -189,6 +195,30 @@ interested in translating it, please email me represents the total interrupt count. You can use this number to figure out if you missed some interrupts. </para> + <para> + For some hardware that has more than one interrupt source internally, + but not separate IRQ mask and status registers, there might be + situations where userspace cannot determine what the interrupt source + was if the kernel handler disables them by writing to the chip's IRQ + register. In such a case, the kernel has to disable the IRQ completely + to leave the chip's register untouched. Now the userspace part can + determine the cause of the interrupt, but it cannot re-enable + interrupts. Another cornercase is chips where re-enabling interrupts + is a read-modify-write operation to a combined IRQ status/acknowledge + register. This would be racy if a new interrupt occurred + simultaneously. + </para> + <para> + To address these problems, UIO also implements a write() function. It + is normally not used and can be ignored for hardware that has only a + single interrupt source or has separate IRQ mask and status registers. + If you need it, however, a write to <filename>/dev/uioX</filename> + will call the <function>irqcontrol()</function> function implemented + by the driver. You have to write a 32-bit value that is usually either + 0 or 1 to disable or enable interrupts. If a driver does not implement + <function>irqcontrol()</function>, <function>write()</function> will + return with <varname>-ENOSYS</varname>. + </para> <para> To handle interrupts properly, your custom kernel module can @@ -362,6 +392,14 @@ device is actually used. <function>open()</function>, you will probably also want a custom <function>release()</function> function. </para></listitem> + +<listitem><para> +<varname>int (*irqcontrol)(struct uio_info *info, s32 irq_on) +</varname>: Optional. If you need to be able to enable or disable +interrupts from userspace by writing to <filename>/dev/uioX</filename>, +you can implement this function. The parameter <varname>irq_on</varname> +will be 0 to disable interrupts and 1 to enable them. +</para></listitem> </itemizedlist> <para> diff --git a/drivers/uio/uio.c b/drivers/uio/uio.c index 5a7ca2e6094..3a6934bf713 100644 --- a/drivers/uio/uio.c +++ b/drivers/uio/uio.c @@ -427,6 +427,31 @@ static ssize_t uio_read(struct file *filep, char __user *buf, return retval; } +static ssize_t uio_write(struct file *filep, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct uio_listener *listener = filep->private_data; + struct uio_device *idev = listener->dev; + ssize_t retval; + s32 irq_on; + + if (idev->info->irq == UIO_IRQ_NONE) + return -EIO; + + if (count != sizeof(s32)) + return -EINVAL; + + if (!idev->info->irqcontrol) + return -ENOSYS; + + if (copy_from_user(&irq_on, buf, count)) + return -EFAULT; + + retval = idev->info->irqcontrol(idev->info, irq_on); + + return retval ? retval : sizeof(s32); +} + static int uio_find_mem_index(struct vm_area_struct *vma) { int mi; @@ -546,6 +571,7 @@ static const struct file_operations uio_fops = { .open = uio_open, .release = uio_release, .read = uio_read, + .write = uio_write, .mmap = uio_mmap, .poll = uio_poll, .fasync = uio_fasync, diff --git a/include/linux/uio_driver.h b/include/linux/uio_driver.h index 973386d439d..cf65e964102 100644 --- a/include/linux/uio_driver.h +++ b/include/linux/uio_driver.h @@ -53,6 +53,7 @@ struct uio_device; * @mmap: mmap operation for this uio device * @open: open operation for this uio device * @release: release operation for this uio device + * @irqcontrol: disable/enable irqs when 0/1 is written to /dev/uioX */ struct uio_info { struct uio_device *uio_dev; @@ -66,6 +67,7 @@ struct uio_info { int (*mmap)(struct uio_info *info, struct vm_area_struct *vma); int (*open)(struct uio_info *info, struct inode *inode); int (*release)(struct uio_info *info, struct inode *inode); + int (*irqcontrol)(struct uio_info *info, s32 irq_on); }; extern int __must_check |