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Subject[PATCH v5 3/5] Add support for receiving USBTMC USB488 SRQ notifications via poll/select
Background:
In many situations operations on multiple instruments need to be
synchronized. poll/select provide a convenient way of waiting on a
number of different instruments and other peripherals
simultaneously.

Signed-off-by: Dave Penkler <dpenkler@gmail.com>
---
drivers/usb/class/usbtmc.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index a95a63d..6294a3c 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -27,6 +27,7 @@
#include <linux/uaccess.h>
#include <linux/kref.h>
#include <linux/slab.h>
+#include <linux/poll.h>
#include <linux/mutex.h>
#include <linux/usb.h>
#include <linux/usb/tmc.h>
@@ -1186,6 +1187,27 @@ static int usbtmc_fasync(int fd, struct file *file, int on)
return fasync_helper(fd, file, on, &data->fasync);
}

+static unsigned int usbtmc_poll(struct file *file, poll_table *wait)
+{
+ struct usbtmc_device_data *data = file->private_data;
+ unsigned int mask;
+
+ mutex_lock(&data->io_mutex);
+
+ if (data->zombie) {
+ mask = POLLHUP | POLLERR;
+ goto no_poll;
+ }
+
+ poll_wait(file, &data->waitq, wait);
+
+ mask = (atomic_read(&data->srq_asserted)) ? POLLIN | POLLRDNORM : 0;
+
+no_poll:
+ mutex_unlock(&data->io_mutex);
+ return mask;
+}
+
static const struct file_operations fops = {
.owner = THIS_MODULE,
.read = usbtmc_read,
@@ -1194,6 +1216,7 @@ static const struct file_operations fops = {
.release = usbtmc_release,
.unlocked_ioctl = usbtmc_ioctl,
.fasync = usbtmc_fasync,
+ .poll = usbtmc_poll,
.llseek = default_llseek,
};

--
2.5.1

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