linux-kernel - Re: [PATCH 6/6] media: hi556: Support device probe in non-zero ACPI D state

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Message-ID: <YbjAHhDFJOSxFI+v@paasikivi.fi.intel.com>
Date:   Tue, 14 Dec 2021 18:02:38 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Bingbu Cao <bingbu.cao@...el.com>
Cc:     linux-media@...r.kernel.org, rafael@...nel.org,
        shawnx.tu@...el.com, tian.shu.qiu@...el.com,
        chiranjeevi.rapolu@...el.com, hyungwoo.yang@...el.com,
        tfiga@...omium.org, senozhatsky@...omium.org,
        linux-kernel@...r.kernel.org, bingbu.cao@...ux.intel.com
Subject: Re: [PATCH 6/6] media: hi556: Support device probe in non-zero ACPI
 D state

Hi Bingbu,

On Tue, Nov 09, 2021 at 04:48:35PM +0800, Bingbu Cao wrote:
> Tell ACPI device PM code that the driver supports the device being in
> non-zero ACPI D state when the driver's probe function is entered.
> 
> Also do identification on the first access of the device, whether in probe
> or when starting streaming.
> 
> Signed-off-by: Bingbu Cao <bingbu.cao@...el.com>
> Signed-off-by: Kao, Arec <arec.kao@...el.com>
> ---
>  drivers/media/i2c/hi556.c | 67 +++++++++++++++++++++++++++++------------------
>  1 file changed, 42 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/media/i2c/hi556.c b/drivers/media/i2c/hi556.c
> index 8db1cbedc1fd..c8011467d1a4 100644
> --- a/drivers/media/i2c/hi556.c
> +++ b/drivers/media/i2c/hi556.c
> @@ -495,6 +495,9 @@ struct hi556 {
>  
>  	/* Streaming on/off */
>  	bool streaming;
> +
> +	/* True if the device has been identified */
> +	bool identified;
>  };
>  
>  static u64 to_pixel_rate(u32 f_index)
> @@ -757,12 +760,38 @@ static void hi556_assign_pad_format(const struct hi556_mode *mode,
>  	fmt->field = V4L2_FIELD_NONE;
>  }
>  
> +static int hi556_identify_module(struct hi556 *hi556)
> +{
> +	struct i2c_client *client = v4l2_get_subdevdata(&hi556->sd);
> +	int ret;
> +	u32 val;

If the sensor's already identified, you can return 0 here.

> +
> +	ret = hi556_read_reg(hi556, HI556_REG_CHIP_ID,
> +			     HI556_REG_VALUE_16BIT, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val != HI556_CHIP_ID) {
> +		dev_err(&client->dev, "chip id mismatch: %x!=%x",
> +			HI556_CHIP_ID, val);
> +		return -ENXIO;
> +	}
> +
> +	hi556->identified = true;
> +
> +	return 0;
> +}

-- 
Sakari Ailus