[PATCH] media: uvcvideo: Add support for changing UVC_URBS/UVC_MAX_PACKETS from sysfs

From: Anurag Kumar Vulisha
Date: Fri Feb 03 2017 - 11:40:33 EST

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The uvc_video.c driver currently has fixed the maximum UVC_URBS queued to 5 and
max UVC_MAX_PACKETS per URB to 32K. This configuration works fine with USB 2.0
and some USB 3.0 cameras on embedded platforms(like Zynq Ultrascale). Since embedded
platforms has slow processing speed as compared to servers/x86 machines, we may need
to increase the number of URBs(UVC_URBS) queued. Also some next generation USB 3.0
cameras (like ZED stereo camera) splits each frame into multiple chunks of 48K bytes
(which is greater than the size of UVC_MAX_PACKETS per URB), so we may need to increase
UVC_MAX_PACKETS also at runtime instead of #define it.

This patch adds the solution to change UVC_URBS and UVC_MAX_PACKETS at runtime using sysfs
layer before starting the video application.

Signed-off-by: Anurag Kumar Vulisha <anuragku@xxxxxxxxxx>
---
drivers/media/usb/uvc/uvc_driver.c | 89 ++++++++++++++++++++++++++++++++++++++
drivers/media/usb/uvc/uvc_video.c | 39 ++++++++++++-----
drivers/media/usb/uvc/uvcvideo.h | 12 +++--
3 files changed, 126 insertions(+), 14 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index 04bf350..51c8058 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -190,6 +190,89 @@ static struct uvc_format_desc uvc_fmts[] = {
},
};

+/* Sysfs attributes for show and store max_urbs/max_packets per URB */
+
+static ssize_t get_max_urbs_show(struct device *dev,
+ struct device_attribute *attr, char *buf) {
+
+ struct uvc_streaming *stream = NULL;
+ struct usb_interface *intf = to_usb_interface(dev);
+ struct uvc_device *udev = usb_get_intfdata(intf);
+ u32 ret_len = 0;
+ u32 stream_num = 0;
+
+ list_for_each_entry(stream, &udev->streams, list) {
+ ret_len += scnprintf((char *)(buf + ret_len), PAGE_SIZE,
+ "stream[%d] = %d\n", stream_num++,
+ stream->max_urbs);
+ }
+
+ return ret_len;
+}
+static DEVICE_ATTR_RO(get_max_urbs);
+
+static ssize_t set_max_urbs_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count) {
+
+ struct uvc_streaming *stream;
+ struct usb_interface *intf = to_usb_interface(dev);
+ struct uvc_device *udev = usb_get_intfdata(intf);
+
+ list_for_each_entry(stream, &udev->streams, list) {
+ sscanf(buf, "%d", &stream->max_urbs);
+ }
+
+ return count;
+}
+static DEVICE_ATTR_WO(set_max_urbs);
+
+static ssize_t get_max_packets_show(struct device *dev,
+ struct device_attribute *attr, char *buf) {
+
+ struct uvc_streaming *stream = NULL;
+ struct usb_interface *intf = to_usb_interface(dev);
+ struct uvc_device *udev = usb_get_intfdata(intf);
+ u32 ret_len = 0;
+ u32 stream_num = 0;
+
+ list_for_each_entry(stream, &udev->streams, list) {
+ ret_len += scnprintf((char *)(buf + ret_len), PAGE_SIZE,
+ "stream[%d] = %d\n", stream_num++,
+ stream->max_packets);
+ }
+
+ return ret_len;
+}
+static DEVICE_ATTR_RO(get_max_packets);
+
+static ssize_t set_max_packets_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count) {
+
+ struct uvc_streaming *stream;
+ struct usb_interface *intf = to_usb_interface(dev);
+ struct uvc_device *udev = usb_get_intfdata(intf);
+
+ list_for_each_entry(stream, &udev->streams, list) {
+ sscanf(buf, "%d", &stream->max_packets);
+ }
+
+ return count;
+}
+static DEVICE_ATTR_WO(set_max_packets);
+
+static struct attribute *uvc_attributes[] = {
+ &dev_attr_get_max_urbs.attr,
+ &dev_attr_set_max_urbs.attr,
+ &dev_attr_get_max_packets.attr,
+ &dev_attr_set_max_packets.attr,
+ NULL
+};
+
+static const struct attribute_group uvc_attr_group = {
+ .attrs = uvc_attributes,
+};
+
+
/* ------------------------------------------------------------------------
* Utility functions
*/
@@ -2097,6 +2180,12 @@ static int uvc_probe(struct usb_interface *intf,
"supported.\n", ret);
}

+ ret = sysfs_create_group(&dev->intf->dev.kobj, &uvc_attr_group);
+ if (ret < 0) {
+ uvc_printk(KERN_ERR, "Failed to create sysfs node %d\n", ret);
+ return ret;
+ }
+
uvc_trace(UVC_TRACE_PROBE, "UVC device initialized.\n");
usb_enable_autosuspend(udev);
return 0;
diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index f3c1c85..18efd03 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1362,7 +1362,7 @@ static void uvc_free_urb_buffers(struct uvc_streaming *stream)
{
unsigned int i;

- for (i = 0; i < UVC_URBS; ++i) {
+ for (i = 0; i < stream->max_urbs; ++i) {
if (stream->urb_buffer[i]) {
#ifndef CONFIG_DMA_NONCOHERENT
usb_free_coherent(stream->dev->udev, stream->urb_size,
@@ -1374,6 +1374,11 @@ static void uvc_free_urb_buffers(struct uvc_streaming *stream)
}
}

+ /* Free memory used for storing URB pointers */
+ kfree(stream->urb);
+ kfree(stream->urb_buffer);
+ kfree(stream->urb_dma);
+
stream->urb_size = 0;
}

@@ -1382,7 +1387,7 @@ static void uvc_free_urb_buffers(struct uvc_streaming *stream)
* already allocated when resuming from suspend, in which case it will
* return without touching the buffers.
*
- * Limit the buffer size to UVC_MAX_PACKETS bulk/isochronous packets. If the
+ * Limit the buffer size to stream->max_packets bulk/isochronous packets. If the
* system is too low on memory try successively smaller numbers of packets
* until allocation succeeds.
*
@@ -1398,16 +1403,24 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream,
if (stream->urb_size)
return stream->urb_size / psize;

+ /* Allocate memory for storing URB pointers */
+ stream->urb = (struct urb **)kcalloc(stream->max_urbs,
+ sizeof(struct urb *), gfp_flags | __GFP_NOWARN);
+ stream->urb_buffer = (char **)kcalloc(stream->max_urbs,
+ sizeof(char *), gfp_flags | __GFP_NOWARN);
+ stream->urb_dma = (dma_addr_t *)kcalloc(stream->max_urbs,
+ sizeof(dma_addr_t), gfp_flags | __GFP_NOWARN);
+
/* Compute the number of packets. Bulk endpoints might transfer UVC
* payloads across multiple URBs.
*/
npackets = DIV_ROUND_UP(size, psize);
- if (npackets > UVC_MAX_PACKETS)
- npackets = UVC_MAX_PACKETS;
+ if (npackets > stream->max_packets)
+ npackets = stream->max_packets;

/* Retry allocations until one succeed. */
for (; npackets > 1; npackets /= 2) {
- for (i = 0; i < UVC_URBS; ++i) {
+ for (i = 0; i < stream->max_urbs; ++i) {
stream->urb_size = psize * npackets;
#ifndef CONFIG_DMA_NONCOHERENT
stream->urb_buffer[i] = usb_alloc_coherent(
@@ -1423,9 +1436,9 @@ static int uvc_alloc_urb_buffers(struct uvc_streaming *stream,
}
}

- if (i == UVC_URBS) {
+ if (i == stream->max_urbs) {
uvc_trace(UVC_TRACE_VIDEO, "Allocated %u URB buffers "
- "of %ux%u bytes each.\n", UVC_URBS, npackets,
+ "of %ux%u bytes each.\n", stream->max_urbs, npackets,
psize);
return npackets;
}
@@ -1446,7 +1459,7 @@ static void uvc_uninit_video(struct uvc_streaming *stream, int free_buffers)

uvc_video_stats_stop(stream);

- for (i = 0; i < UVC_URBS; ++i) {
+ for (i = 0; i < stream->max_urbs; ++i) {
urb = stream->urb[i];
if (urb == NULL)
continue;
@@ -1507,7 +1520,7 @@ static int uvc_init_video_isoc(struct uvc_streaming *stream,

size = npackets * psize;

- for (i = 0; i < UVC_URBS; ++i) {
+ for (i = 0; i < stream->max_urbs; ++i) {
urb = usb_alloc_urb(npackets, gfp_flags);
if (urb == NULL) {
uvc_uninit_video(stream, 1);
@@ -1573,7 +1586,7 @@ static int uvc_init_video_bulk(struct uvc_streaming *stream,
if (stream->type == V4L2_BUF_TYPE_VIDEO_OUTPUT)
size = 0;

- for (i = 0; i < UVC_URBS; ++i) {
+ for (i = 0; i < stream->max_urbs; ++i) {
urb = usb_alloc_urb(0, gfp_flags);
if (urb == NULL) {
uvc_uninit_video(stream, 1);
@@ -1678,7 +1691,7 @@ static int uvc_init_video(struct uvc_streaming *stream, gfp_t gfp_flags)
return ret;

/* Submit the URBs. */
- for (i = 0; i < UVC_URBS; ++i) {
+ for (i = 0; i < stream->max_urbs; ++i) {
ret = usb_submit_urb(stream->urb[i], gfp_flags);
if (ret < 0) {
uvc_printk(KERN_ERR, "Failed to submit URB %u "
@@ -1839,6 +1852,10 @@ int uvc_video_init(struct uvc_streaming *stream)
stream->cur_format = format;
stream->cur_frame = frame;

+ /* Set max URB numbers & max packets per URB to default */
+ stream->max_urbs = UVC_URBS;
+ stream->max_packets = UVC_MAX_PACKETS;
+
/* Select the video decoding function */
if (stream->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
if (stream->dev->quirks & UVC_QUIRK_BUILTIN_ISIGHT)
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 3d6cc62..250cf89 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -506,9 +506,15 @@ struct uvc_streaming {
__u32 max_payload_size;
} bulk;

- struct urb *urb[UVC_URBS];
- char *urb_buffer[UVC_URBS];
- dma_addr_t urb_dma[UVC_URBS];
+ /* Maximum number of URBs that can be submitted */
+ u32 max_urbs;
+
+ /* Maximum number of packets per URB */
+ u32 max_packets;
+
+ struct urb **urb;
+ char **urb_buffer;
+ dma_addr_t *urb_dma;
unsigned int urb_size;

__u32 sequence;
--
2.1.1

Next message: Miroslav Benes: "Re: [PATCH v4 13/15] livepatch: change to a per-task consistency model"
Previous message: Juergen Gross: "Re: [PATCH v2 4/9] xen/pvh: Bootstrap PVH guest"
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