linux-kernel - Re: [PATCH v2 1/2] media: i2c: imx290: Check for availability in probe()

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Message-ID: <ZtBss-c1IN7j-Nf5@kekkonen.localdomain>
Date: Thu, 29 Aug 2024 12:42:27 +0000
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: Benjamin Bara <bbara93@...il.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Hans de Goede <hdegoede@...hat.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Alexander Stein <alexander.stein@...tq-group.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	Benjamin Bara <benjamin.bara@...data.com>
Subject: Re: [PATCH v2 1/2] media: i2c: imx290: Check for availability in
 probe()

Hi Benjamin,

On Wed, Aug 28, 2024 at 08:13:07PM +0200, Benjamin Bara wrote:
> Currently, the V4L2 subdevice is also created when the device is not
> available/connected. In this case, dmesg shows the following:
> 
> [   10.419510] imx290 7-001a: Error writing reg 0x301c: -6
> [   10.428981] imx290 7-001a: Error writing reg 0x3020: -6
> [   10.442712] imx290 7-001a: Error writing reg 0x3018: -6
> [   10.454018] imx290 7-001a: Error writing reg 0x3020: -6
> 
> which seems to come from imx290_ctrl_update() after the subdev init is
> finished. However, as the errors are ignored, the subdev is initialized
> but simply does not work. From userspace perspective, there is no
> visible difference between a working and not-working subdevice (except
> when trying it out or watching for the error message).
> 
> This commit adds a simple availability check before starting with the
> subdev initialization to error out instead.
> 
> Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
> ---
> Changes since v1:
> - define operating/standby mode and use it
> - read out the standby mode during probe and ensure it is standby
> ---
>  drivers/media/i2c/imx290.c | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/i2c/imx290.c b/drivers/media/i2c/imx290.c
> index 4150e6e4b9a6..2a869576600c 100644
> --- a/drivers/media/i2c/imx290.c
> +++ b/drivers/media/i2c/imx290.c
> @@ -29,6 +29,8 @@
>  #include <media/v4l2-subdev.h>
>  
>  #define IMX290_STANDBY					CCI_REG8(0x3000)
> +#define IMX290_STANDBY_OPERATING			(0 << 0)
> +#define IMX290_STANDBY_STANDBY				(1 << 0)

This should use BIT() instead (or at least unsigned values). I'll fix that
while at it, too...

-- 
Kind regards,

Sakari Ailus