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Message-ID: <ee6e4732-0d71-4e96-8832-f4251540fd53@jjverkuil.nl>
Date: Wed, 30 Apr 2025 15:03:26 +0200
From: Hans Verkuil <hans@...erkuil.nl>
To: Ricardo Ribalda <ribalda@...omium.org>, Hans Verkuil <hverkuil@...all.nl>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Hans de Goede <hdegoede@...hat.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>, linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7] media: uvcvideo: Set V4L2_CTRL_FLAG_DISABLED during
queryctrl errors
Hi Ricardo,
Apologies, this got snowed under.
On 07/04/2025 16:39, Ricardo Ribalda wrote:
> Hi Hans
>
> On Mon, 7 Apr 2025 at 16:02, Hans Verkuil <hverkuil@...all.nl> wrote:
>>
>> Hi Ricardo,
>>
>> Some more comments:
>>
>> On 03/04/2025 14:59, Ricardo Ribalda wrote:
>>> To implement VIDIOC_QUERYCTRL, we need to know the minimum, maximum,
>>> step and flags of the control. For some of the controls, this involves
>>> querying the actual hardware.
>>>
>>> Some non-compliant cameras produce errors when we query them. These
>>> error can be triggered every time, sometimes, or when other controls do
>>> not have the "right value". Right now, we populate that error to userspace.
>>> When an error happens, the v4l2 framework does not copy the v4l2_queryctrl
>>> struct to userspace. Also, userspace apps are not ready to handle any
>>> other error than -EINVAL.
>>>
>>> One of the main usecases of VIDIOC_QUERYCTRL is enumerating the controls
>>> of a device. This is done using the V4L2_CTRL_FLAG_NEXT_CTRL flag. In
>>> that usecase, a non-compliant control will make it almost impossible to
>>> enumerate all controls of the device.
>>>
>>> A control with an invalid max/min/step/flags is better than non being
>>> able to enumerate the rest of the controls.
>>>
>>> This patch:
>>> - Retries for an extra attempt to read the control, to avoid spurious
>>> errors. More attempts do not seem to produce better results in the
>>> tested hardware.
>>> - Makes VIDIOC_QUERYCTRL return 0 in all the error cases different than
>>> -EINVAL.
>>> - Introduces a warning in dmesg so we can have a trace of what has happened
>>> and sets the V4L2_CTRL_FLAG_DISABLED.
>>> - Makes sure we keep returning V4L2_CTRL_FLAG_DISABLED for all the next
>>> attempts to query that control (other operations have the same
>>> functionality as now).
>>>
>>> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
>>> ---
>>> Hi 2*Hans and Laurent!
>>>
>>> I came around a device that was listing just a couple of controls when
>>> it should be listing much more.
>>>
>>> Some debugging later I found that the device was returning -EIO when
>>> all the focal controls were read.
>>>
>>> Lots of good arguments in favor/against this patch in the v1. Please
>>> check!
>>>
>>> Without this patch:
>>> $ v4l2-ctl --list-ctrls
>>> User Controls
>>>
>>> brightness 0x00980900 (int) : min=0 max=255 step=1 default=128 value=128
>>> contrast 0x00980901 (int) : min=0 max=100 step=1 default=32 value=32
>>> saturation 0x00980902 (int) : min=0 max=100 step=1 default=64 value=64
>>> hue 0x00980903 (int) : min=-180 max=180 step=1 default=0 value=0
>>> white_balance_automatic 0x0098090c (bool) : default=1 value=1
>>> gamma 0x00980910 (int) : min=90 max=150 step=1 default=120 value=120
>>> power_line_frequency 0x00980918 (menu) : min=0 max=2 default=2 value=2 (60 Hz)
>>> white_balance_temperature 0x0098091a (int) : min=2800 max=6500 step=1 default=4600 value=4600 flags=inactive
>>>
>>> With this patch:
>>> $ v4l2-ctl --list-ctrls
>>>
>>> User Controls
>>>
>>> brightness 0x00980900 (int) : min=0 max=255 step=1 default=128 value=128
>>> contrast 0x00980901 (int) : min=0 max=100 step=1 default=32 value=32
>>> saturation 0x00980902 (int) : min=0 max=100 step=1 default=64 value=64
>>> hue 0x00980903 (int) : min=-180 max=180 step=1 default=0 value=0
>>> white_balance_automatic 0x0098090c (bool) : default=1 value=1
>>> gamma 0x00980910 (int) : min=90 max=150 step=1 default=120 value=120
>>> power_line_frequency 0x00980918 (menu) : min=0 max=2 default=2 value=2 (60 Hz)
>>> white_balance_temperature 0x0098091a (int) : min=2800 max=6500 step=1 default=4600 value=4600 flags=inactive
>>> sharpness 0x0098091b (int) : min=0 max=7 step=1 default=3 value=3
>>> backlight_compensation 0x0098091c (int) : min=0 max=2 step=1 default=1 value=1
>>> [ 32.777643] usb 3-6: UVC non compliance: permanently disabling control 98091b (Sharpness), due to error -5
>>>
>>> Camera Controls
>>>
>>> auto_exposure 0x009a0901 (menu) : min=0 max=3 default=3 value=3 (Aperture Priority Mode)
>>> exposure_time_absolute 0x009a0902 (int) : min=2 max=1250 step=1 default=156 value=156 flags=inactive
>>> exposure_dynamic_framerate 0x009a0903 (bool) : default=0 value=0
>>> privacy 0x009a0910 (bool) : default=0 value=0 flags=read-only
>>> region_of_interest_rectangle 0x009a1901 (unknown): type=107 value=unsupported payload type flags=has-payload
>>> region_of_interest_auto_ctrls 0x009a1902 (bitmask): max=0x00000001 default=0x00000001 value=1
>>
>> When you post a v8, remember to update the v4l2-ctl --list-ctrls output.
>
> will do. Please note that the output is after --- so it will not be in
> git log. Let me know if I shall promote it.
It's fine after the ---.
>
>>
>>>
>>> Emulating error with:
>>> + if (cs == UVC_PU_SHARPNESS_CONTROL && query == UVC_GET_MAX) {
>>> + printk(KERN_ERR "%s:%d %s\n", __FILE__, __LINE__, __func__);
>>> + return -EIO;
>>> + }
>>> In uvc_query_ctrl()
>>> ---
>>> Changes in v7:
>>> - Only retry on -EIO (Thanks Hans).
>>> - Add comment for retry (Thanks Hans).
>>> - Rebase patch
>>> - Check master_map->disabled before reading the master control.
>>> - Link to v6: https://lore.kernel.org/r/20250310-uvc-eaccess-v6-1-bf4562f7cabd@chromium.org
>>>
>>> Changes in v6:
>>> - Keep returning V4L2_CTRL_FLAG_DISABLED in future control queries.
>>> - Link to v5: https://lore.kernel.org/r/20250224-uvc-eaccess-v5-1-690d73bcef28@chromium.org
>>>
>>> Changes in v5:
>>> - Explain the retry in the commit message (Thanks Laurent).
>>> - Link to v4: https://lore.kernel.org/r/20250111-uvc-eaccess-v4-1-c7759bfd1bd4@chromium.org
>>>
>>> Changes in v4:
>>> - Display control name (Thanks Hans)
>>> - Link to v3: https://lore.kernel.org/r/20250107-uvc-eaccess-v3-1-99f3335d5133@chromium.org
>>>
>>> Changes in v3:
>>> - Add a retry mechanism during error.
>>> - Set V4L2_CTRL_FLAG_DISABLED flag.
>>> - Link to v2: https://lore.kernel.org/r/20241219-uvc-eaccess-v2-1-bf6520c8b86d@chromium.org
>>>
>>> Changes in v2:
>>> - Never return error, even if we are not enumerating the controls
>>> - Improve commit message.
>>> - Link to v1: https://lore.kernel.org/r/20241213-uvc-eaccess-v1-1-62e0b4fcc634@chromium.org
>>> ---
>>> drivers/media/usb/uvc/uvc_ctrl.c | 53 ++++++++++++++++++++++++++++++++++------
>>> drivers/media/usb/uvc/uvcvideo.h | 2 ++
>>> 2 files changed, 47 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
>>> index cbf19aa1d82374a08cf79b6a6787fa348b83523a..b41fed364d54aefd7da72c47197cf9d9e3c1b176 100644
>>> --- a/drivers/media/usb/uvc/uvc_ctrl.c
>>> +++ b/drivers/media/usb/uvc/uvc_ctrl.c
>>> @@ -1483,14 +1483,28 @@ static u32 uvc_get_ctrl_bitmap(struct uvc_control *ctrl,
>>> return ~0;
>>> }
>>>
>>> +/*
>>> + * Maximum retry count to avoid spurious errors with controls. Increase this
>>
>> Increase -> Increasing
>>
>>> + * value does no seem to produce better results in the tested hardware.
>>> + */
>>> +#define MAX_QUERY_RETRIES 2
>>> +
>>> static int __uvc_queryctrl_boundaries(struct uvc_video_chain *chain,
>>> struct uvc_control *ctrl,
>>> struct uvc_control_mapping *mapping,
>>> struct v4l2_query_ext_ctrl *v4l2_ctrl)
>>> {
>>> if (!ctrl->cached) {
>>> - int ret = uvc_ctrl_populate_cache(chain, ctrl);
>>> - if (ret < 0)
>>> + unsigned int retries;
>>> + int ret;
>>> +
>>> + for (retries = 0; retries < MAX_QUERY_RETRIES; retries++) {
>>> + ret = uvc_ctrl_populate_cache(chain, ctrl);
>>> + if (ret != -EIO)
>>> + break;
>>> + }
>>> +
>>> + if (ret)
>>> return ret;
>>> }
>>>
>>> @@ -1567,6 +1581,7 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>>> {
>>> struct uvc_control_mapping *master_map = NULL;
>>> struct uvc_control *master_ctrl = NULL;
>>> + int ret;
>>>
>>> memset(v4l2_ctrl, 0, sizeof(*v4l2_ctrl));
>>> v4l2_ctrl->id = mapping->id;
>>> @@ -1587,18 +1602,29 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>>> __uvc_find_control(ctrl->entity, mapping->master_id,
>>> &master_map, &master_ctrl, 0, 0);
>>> if (master_ctrl && (master_ctrl->info.flags & UVC_CTRL_FLAG_GET_CUR)) {
>>> + unsigned int retries;
>>> s32 val;
>>> int ret;
>>>
>>> if (WARN_ON(uvc_ctrl_mapping_is_compound(master_map)))
>>> return -EIO;
>>>
>>> - ret = __uvc_ctrl_get(chain, master_ctrl, master_map, &val);
>>> - if (ret < 0)
>>> - return ret;
>>> + for (retries = 0; retries < MAX_QUERY_RETRIES; retries++) {
>>> + ret = __uvc_ctrl_get(chain, master_ctrl, master_map,
>>> + &val);
>>
>> I'd write this:
>>
>> if (ret < 0 && ret != -EIO)
>> return ret;
>>
>> Without that you'll see the non compliance warning below, but that's not
>> what you want for non-EIO errors.
>
> I am not sure about this one. If there is an error reading a master
> control you probably want to continue. Semantically it is similar to
> not finding the control or having invalid flags. And in those two
> cases we move on.
> Also, I think there is some value for the warning. It is counter
> intuitive that query_ctrl for control X fails due to an error in
> control Y.
In the original code you just return the error as well, without a
warning.
I think for non-EIO errors you should just return. It can always be
changed later, for now I think we should stick close to the original
code.
It's really a matter of taste rather than right or wrong code.
Regards,
Hans
>
> Let me know what do you think.
>
>>
>>> + if (ret != -EIO)
>>> + break;
>>> + }
>>>
>>> - if (val != mapping->master_manual)
>>> - v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
>>> + if (ret < 0) {
>>> + dev_warn_ratelimited(&chain->dev->udev->dev,
>>> + "UVC non compliance: Error %d querying master control %x (%s)\n",
>>> + ret, master_map->id,
>>> + uvc_map_get_name(master_map));
>>> + } else {
>>> + if (val != mapping->master_manual)
>>> + v4l2_ctrl->flags |= V4L2_CTRL_FLAG_INACTIVE;
>>> + }
>>> }
>>>
>>> v4l2_ctrl->elem_size = uvc_mapping_v4l2_size(mapping);
>>> @@ -1613,7 +1639,18 @@ static int __uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>>> return 0;
>>> }
>>>
>>> - return __uvc_queryctrl_boundaries(chain, ctrl, mapping, v4l2_ctrl);
>>> + ret = __uvc_queryctrl_boundaries(chain, ctrl, mapping, v4l2_ctrl);
>>> + if (ret && !mapping->disabled) {
>>> + dev_warn(&chain->dev->udev->dev,
>>> + "UVC non compliance: permanently disabling control %x (%s), due to error %d\n",
>>> + mapping->id, uvc_map_get_name(mapping), ret);
>>> + mapping->disabled = true;
>>> + }
>>> +
>>> + if (mapping->disabled)
>>> + v4l2_ctrl->flags |= V4L2_CTRL_FLAG_DISABLED;
>>> +
>>> + return 0;
>>> }
>>>
>>> int uvc_query_v4l2_ctrl(struct uvc_video_chain *chain,
>>> diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
>>> index b4ee701835fc016474d2cd2a0b67b2aa915c1c60..8e3753896d42baddcc2192057e8c5786ddd79fa8 100644
>>> --- a/drivers/media/usb/uvc/uvcvideo.h
>>> +++ b/drivers/media/usb/uvc/uvcvideo.h
>>> @@ -134,6 +134,8 @@ struct uvc_control_mapping {
>>> s32 master_manual;
>>> u32 slave_ids[2];
>>>
>>> + bool disabled;
>>> +
>>> const struct uvc_control_mapping *(*filter_mapping)
>>> (struct uvc_video_chain *chain,
>>> struct uvc_control *ctrl);
>>>
>>> ---
>>> base-commit: 4e82c87058f45e79eeaa4d5bcc3b38dd3dce7209
>>> change-id: 20250403-uvc-eaccess-8f3666151830
>>>
>>> Best regards,
>>
>> Regards,
>>
>> Hans
>
>
>
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