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SubjectRe: [PATCH] media: uvcvideo: Do not alloc dev->status
Hi Ricardo,

Thank you for the patch.

On Wed, Dec 14, 2022 at 12:23:41PM +0100, Ricardo Ribalda wrote:
> UVC_MAX_STATUS_SIZE is 16, simplify the code by inlining dev->status.

The reason why uvc_status is allocated dynamically is to ensure cache
line alignment, as the USB host controller may DMA to the buffer.

> Now that we are at it, remove all the castings.
>
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
> To: Yunke Cao <yunkec@chromium.org>
> To: Sergey Senozhatsky <senozhatsky@chromium.org>
> To: Max Staudt <mstaudt@google.com>
> To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> To: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: linux-media@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
> drivers/media/usb/uvc/uvc_status.c | 69 ++++++++++++--------------------------
> drivers/media/usb/uvc/uvcvideo.h | 22 +++++++++++-
> 2 files changed, 42 insertions(+), 49 deletions(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
> index 7518ffce22ed..adf63e7616c9 100644
> --- a/drivers/media/usb/uvc/uvc_status.c
> +++ b/drivers/media/usb/uvc/uvc_status.c
> @@ -73,38 +73,24 @@ static void uvc_input_report_key(struct uvc_device *dev, unsigned int code,
> /* --------------------------------------------------------------------------
> * Status interrupt endpoint
> */
> -struct uvc_streaming_status {
> - u8 bStatusType;
> - u8 bOriginator;
> - u8 bEvent;
> - u8 bValue[];
> -} __packed;
> -
> -struct uvc_control_status {
> - u8 bStatusType;
> - u8 bOriginator;
> - u8 bEvent;
> - u8 bSelector;
> - u8 bAttribute;
> - u8 bValue[];
> -} __packed;
> -
> static void uvc_event_streaming(struct uvc_device *dev,
> - struct uvc_streaming_status *status, int len)
> + struct uvc_status *status, int len)
> {
> - if (len < 3) {
> + if (len <= offsetof(struct uvc_status, bEvent)) {
> uvc_dbg(dev, STATUS,
> "Invalid streaming status event received\n");
> return;
> }
>
> if (status->bEvent == 0) {
> - if (len < 4)
> + if (len <= offsetof(struct uvc_status, streaming))
> return;
> +
> uvc_dbg(dev, STATUS, "Button (intf %u) %s len %d\n",
> status->bOriginator,
> - status->bValue[0] ? "pressed" : "released", len);
> - uvc_input_report_key(dev, KEY_CAMERA, status->bValue[0]);
> + status->streaming.button ? "pressed" : "released", len);
> + uvc_input_report_key(dev, KEY_CAMERA,
> + status->streaming.button);
> } else {
> uvc_dbg(dev, STATUS, "Stream %u error event %02x len %d\n",
> status->bOriginator, status->bEvent, len);
> @@ -131,7 +117,7 @@ static struct uvc_control *uvc_event_entity_find_ctrl(struct uvc_entity *entity,
> }
>
> static struct uvc_control *uvc_event_find_ctrl(struct uvc_device *dev,
> - const struct uvc_control_status *status,
> + const struct uvc_status *status,
> struct uvc_video_chain **chain)
> {
> list_for_each_entry((*chain), &dev->chains, list) {
> @@ -143,7 +129,7 @@ static struct uvc_control *uvc_event_find_ctrl(struct uvc_device *dev,
> continue;
>
> ctrl = uvc_event_entity_find_ctrl(entity,
> - status->bSelector);
> + status->control.bSelector);
> if (ctrl)
> return ctrl;
> }
> @@ -153,7 +139,7 @@ static struct uvc_control *uvc_event_find_ctrl(struct uvc_device *dev,
> }
>
> static bool uvc_event_control(struct urb *urb,
> - const struct uvc_control_status *status, int len)
> + const struct uvc_status *status, int len)
> {
> static const char *attrs[] = { "value", "info", "failure", "min", "max" };
> struct uvc_device *dev = urb->context;
> @@ -161,24 +147,24 @@ static bool uvc_event_control(struct urb *urb,
> struct uvc_control *ctrl;
>
> if (len < 6 || status->bEvent != 0 ||
> - status->bAttribute >= ARRAY_SIZE(attrs)) {
> + status->control.bAttribute >= ARRAY_SIZE(attrs)) {
> uvc_dbg(dev, STATUS, "Invalid control status event received\n");
> return false;
> }
>
> uvc_dbg(dev, STATUS, "Control %u/%u %s change len %d\n",
> - status->bOriginator, status->bSelector,
> - attrs[status->bAttribute], len);
> + status->bOriginator, status->control.bSelector,
> + attrs[status->control.bAttribute], len);
>
> /* Find the control. */
> ctrl = uvc_event_find_ctrl(dev, status, &chain);
> if (!ctrl)
> return false;
>
> - switch (status->bAttribute) {
> + switch (status->control.bAttribute) {
> case UVC_CTRL_VALUE_CHANGE:
> return uvc_ctrl_status_event_async(urb, chain, ctrl,
> - status->bValue);
> + status->control.bValue);
>
> case UVC_CTRL_INFO_CHANGE:
> case UVC_CTRL_FAILURE_CHANGE:
> @@ -214,28 +200,22 @@ static void uvc_status_complete(struct urb *urb)
>
> len = urb->actual_length;
> if (len > 0) {
> - switch (dev->status[0] & 0x0f) {
> + switch (dev->status.bStatusType & 0x0f) {
> case UVC_STATUS_TYPE_CONTROL: {
> - struct uvc_control_status *status =
> - (struct uvc_control_status *)dev->status;
> -
> - if (uvc_event_control(urb, status, len))
> + if (uvc_event_control(urb, &dev->status, len))
> /* The URB will be resubmitted in work context. */
> return;
> break;
> }
>
> case UVC_STATUS_TYPE_STREAMING: {
> - struct uvc_streaming_status *status =
> - (struct uvc_streaming_status *)dev->status;
> -
> - uvc_event_streaming(dev, status, len);
> + uvc_event_streaming(dev, &dev->status, len);
> break;
> }
>
> default:
> uvc_dbg(dev, STATUS, "Unknown status event type %u\n",
> - dev->status[0]);
> + dev->status.bStatusType);
> break;
> }
> }
> @@ -259,15 +239,9 @@ int uvc_status_init(struct uvc_device *dev)
>
> uvc_input_init(dev);
>
> - dev->status = kzalloc(UVC_MAX_STATUS_SIZE, GFP_KERNEL);
> - if (dev->status == NULL)
> - return -ENOMEM;
> -
> dev->int_urb = usb_alloc_urb(0, GFP_KERNEL);
> - if (dev->int_urb == NULL) {
> - kfree(dev->status);
> + if (!dev->int_urb)
> return -ENOMEM;
> - }
>
> pipe = usb_rcvintpipe(dev->udev, ep->desc.bEndpointAddress);
>
> @@ -281,7 +255,7 @@ int uvc_status_init(struct uvc_device *dev)
> interval = fls(interval) - 1;
>
> usb_fill_int_urb(dev->int_urb, dev->udev, pipe,
> - dev->status, UVC_MAX_STATUS_SIZE, uvc_status_complete,
> + &dev->status, sizeof(dev->status), uvc_status_complete,
> dev, interval);
>
> return 0;
> @@ -296,7 +270,6 @@ void uvc_status_unregister(struct uvc_device *dev)
> void uvc_status_cleanup(struct uvc_device *dev)
> {
> usb_free_urb(dev->int_urb);
> - kfree(dev->status);
> }
>
> int uvc_status_start(struct uvc_device *dev, gfp_t flags)
> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
> index df93db259312..cdd2e328acc2 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -527,6 +527,26 @@ struct uvc_device_info {
> const struct uvc_control_mapping **mappings;
> };
>
> +struct uvc_status_streaming {
> + u8 button;
> +} __packed;
> +
> +struct uvc_status_control {
> + u8 bSelector;
> + u8 bAttribute;
> + u8 bValue[11];
> +} __packed;
> +
> +struct uvc_status {
> + u8 bStatusType;
> + u8 bOriginator;
> + u8 bEvent;
> + union {
> + struct uvc_status_control control;
> + struct uvc_status_streaming streaming;
> + };
> +} __packed;
> +
> struct uvc_device {
> struct usb_device *udev;
> struct usb_interface *intf;
> @@ -559,7 +579,7 @@ struct uvc_device {
> /* Status Interrupt Endpoint */
> struct usb_host_endpoint *int_ep;
> struct urb *int_urb;
> - u8 *status;
> + struct uvc_status status;
> struct input_dev *input;
> char input_phys[64];
>
>
> ---
> base-commit: 0ec5a38bf8499f403f81cb81a0e3a60887d1993c
> change-id: 20221214-uvc-status-alloc-93becb783898

--
Regards,

Laurent Pinchart

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