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Subject[PATCH v5 2/5] Add support for USBTMC USB488 SRQ notification with fasync
Background:
By configuring an instrument's event status register various
conditions can be reported via an SRQ notification. This complements
the synchronous polling approach using the READ_STATUS_BYTE ioctl
with an asynchronous notification.

Signed-off-by: Dave Penkler <dpenkler@gmail.com>
---
drivers/usb/class/usbtmc.c | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index 60a71cb..a95a63d 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -99,6 +99,7 @@ struct usbtmc_device_data {
int iin_interval;
struct urb *iin_urb;
u16 iin_wMaxPacketSize;
+ atomic_t srq_asserted;

u8 rigol_quirk;

@@ -113,6 +114,7 @@ struct usbtmc_device_data {
struct kref kref;
struct mutex io_mutex; /* only one i/o function running at a time */
wait_queue_head_t waitq;
+ struct fasync_struct *fasync;
};
#define to_usbtmc_data(d) container_of(d, struct usbtmc_device_data, kref)

@@ -404,6 +406,9 @@ static int usbtmc488_ioctl_read_stb(struct usbtmc_device_data *data,

atomic_set(&data->iin_data_valid, 0);

+ /* must issue read_stb before using poll or select */
+ atomic_set(&data->srq_asserted, 0);
+
rv = usb_control_msg(data->usb_dev,
usb_rcvctrlpipe(data->usb_dev, 0),
USBTMC488_REQUEST_READ_STATUS_BYTE,
@@ -1174,6 +1179,13 @@ skip_io_on_zombie:
return retval;
}

+static int usbtmc_fasync(int fd, struct file *file, int on)
+{
+ struct usbtmc_device_data *data = file->private_data;
+
+ return fasync_helper(fd, file, on, &data->fasync);
+}
+
static const struct file_operations fops = {
.owner = THIS_MODULE,
.read = usbtmc_read,
@@ -1181,6 +1193,7 @@ static const struct file_operations fops = {
.open = usbtmc_open,
.release = usbtmc_release,
.unlocked_ioctl = usbtmc_ioctl,
+ .fasync = usbtmc_fasync,
.llseek = default_llseek,
};

@@ -1210,6 +1223,16 @@ static void usbtmc_interrupt(struct urb *urb)
wake_up_interruptible(&data->waitq);
goto exit;
}
+ /* check for SRQ notification */
+ if ((data->iin_buffer[0] & 0x7f) == 1) {
+ if (data->fasync)
+ kill_fasync(&data->fasync,
+ SIGIO, POLL_IN);
+
+ atomic_set(&data->srq_asserted, 1);
+ wake_up_interruptible(&data->waitq);
+ goto exit;
+ }
}
dev_warn(&data->intf->dev, "invalid notification: %x\n",
data->iin_buffer[0]);
@@ -1274,6 +1297,7 @@ static int usbtmc_probe(struct usb_interface *intf,
mutex_init(&data->io_mutex);
init_waitqueue_head(&data->waitq);
atomic_set(&data->iin_data_valid, 0);
+ atomic_set(&data->srq_asserted, 0);
data->zombie = 0;

/* Determine if it is a Rigol or not */
--
2.5.1

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