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Date:   Tue, 20 Jun 2023 12:39:42 +0200
From:   Tommaso Merciai <tomm.merciai@gmail.com>
To:     Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc:     Sakari Ailus <sakari.ailus@linux.intel.com>,
        jacopo.mondi@ideasonboard.com, martin.hecht@avnet.eu,
        michael.roeder@avnet.eu, linuxfancy@googlegroups.com,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Hans Verkuil <hverkuil@xs4all.nl>,
        Marco Felsch <m.felsch@pengutronix.de>,
        Gerald Loacker <gerald.loacker@wolfvision.net>,
        Nicholas Roth <nicholas@rothemail.net>,
        Krzysztof =?utf-8?Q?Ha=C5=82asa?= <khalasa@piap.pl>,
        Linus Walleij <linus.walleij@linaro.org>,
        Benjamin Mugnier <benjamin.mugnier@foss.st.com>,
        Mikhail Rudenko <mike.rudenko@gmail.com>,
        Shawn Tu <shawnx.tu@intel.com>, linux-kernel@vger.kernel.org,
        linux-media@vger.kernel.org
Subject: Re: [PATCH v5 3/3] media: i2c: Add support for alvium camera
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Hi Laurent, Sakari,
Thanks for your comment.

On Tue, Jun 20, 2023 at 12:43:28PM +0300, Laurent Pinchart wrote:
> On Tue, Jun 20, 2023 at 06:54:43AM +0200, Tommaso Merciai wrote:
> > On Mon, Jun 19, 2023 at 05:24:58PM +0300, Laurent Pinchart wrote:
> > > On Mon, Jun 19, 2023 at 10:50:10AM +0000, Sakari Ailus wrote:
> > > > On Fri, Jun 09, 2023 at 03:09:41PM +0200, Tommaso Merciai wrote:
> > > > > On Fri, Jun 09, 2023 at 09:17:42AM +0000, Sakari Ailus wrote:
> > > > > > On Thu, Jun 08, 2023 at 10:31:16AM +0200, Tommaso Merciai wrote:
> > > > > > > The Alvium camera is shipped with sensor + isp in the same housing.
> > > > > > > The camera can be equipped with one out of various sensor and abstract
> > > > > > > the user from this. Camera is connected via MIPI CSI-2.
> > > > > > > 
> > > > > > > Most of the camera module features are supported, with the main exception
> > > > > > > being fw update.
> > > > > > > 
> > > > > > > The driver provides all mandatory, optional and recommended V4L2 controls
> > > > > > > for maximum compatibility with libcamera
> > > > > > > 
> > > > > > > References:
> > > > > > >  - https://www.alliedvision.com/en/products/embedded-vision-solutions
> > > > > > > 
> > > > > > > Signed-off-by: Tommaso Merciai <tomm.merciai@gmail.com>
> > > > > > > ---
> > > > > > > Changes since v2:
> > > > > > >  - Removed gpios/clock handling as suggested by LPinchart
> > > > > > >  - Added vcc-ext-in supply support as suggested by LPinchart
> > > > > > >  - Fixed alvium_setup_mipi_fmt funct as suggested by CJAILLET
> > > > > > >  - Removed upside_down/hshake_bit priv data as suggested by CJAILLET
> > > > > > >  - Fixed commit body as suggested by LPinchart
> > > > > > >  - Mv alvium_set_streamon_delay to yalvium_set_lp2hs_delay
> > > > > > >  - Fixed comment on lp2hs prop as suggested by LPinchart
> > > > > > >  - Added pm resume/suspend functs as suggested by LPinchart
> > > > > > >  - Dropped alvium_link_setup/alvium_s_power as suggested by LPinchart
> > > > > > >  - Fixed regs defines as suggested by LPinchart
> > > > > > >  - Fixed typedef as suggested by LPinchart
> > > > > > >  - Dropped bcrm_v/fw_v from priv data as suggested by LPinchart
> > > > > > >  - Now driver use the subdev active state to store the active format and crop
> > > > > > >    as suggested by LPinchart
> > > > > > >  - Dropped alvium_is_csi2/i2c_to_alvium as suggested by LPinchart
> > > > > > > 
> > > > > > > Changes since v3:
> > > > > > >  - Fixed warnings Reported-by: kernel test robot <lkp@intel.com>
> > > > > > > 
> > > > > > > Changes since v4:
> > > > > > >  - Removed print into alvium_get_dt_data for alliedvision,lp2hs-delay-us as
> > > > > > >    suggested by CDooley
> > > > > > > 
> > > > > > >  drivers/media/i2c/Kconfig       |   10 +
> > > > > > >  drivers/media/i2c/Makefile      |    1 +
> > > > > > >  drivers/media/i2c/alvium-csi2.c | 3479 +++++++++++++++++++++++++++++++
> > > > > > >  drivers/media/i2c/alvium-csi2.h |  485 +++++
> > > > > > >  4 files changed, 3975 insertions(+)
> > > > > > >  create mode 100644 drivers/media/i2c/alvium-csi2.c
> > > > > > >  create mode 100644 drivers/media/i2c/alvium-csi2.h
> > > 
> > > [snip]
> > > 
> > > > > > > diff --git a/drivers/media/i2c/alvium-csi2.c b/drivers/media/i2c/alvium-csi2.c
> > > > > > > new file mode 100644
> > > > > > > index 000000000000..52c9263075cf
> > > > > > > --- /dev/null
> > > > > > > +++ b/drivers/media/i2c/alvium-csi2.c
> > > > > > > @@ -0,0 +1,3479 @@
> > > 
> > > [snip]
> > > 
> > > > > > > +static int alvium_get_img_width_params(struct alvium_dev *alvium)
> > > > > > > +{
> > > > > > > +	struct device *dev = &alvium->i2c_client->dev;
> > > > > > > +	int ret;
> > > > > > > +	u64 val;
> > > > > > > +
> > > > > > > +	if (!alvium->bcrm_addr)
> > > > > > > +		return -EINVAL;
> > > > > > > +
> > > > > > > +	ret = alvium_read(alvium,
> > > > > > > +			  REG_BCRM_IMG_WIDTH_MIN_R,
> > > > > > > +			  &val);
> > > > > > > +	if (ret) {
> > > > > > > +		dev_err(dev, "Fail to read img min width reg\n");
> > > > > > > +		return ret;
> > > > > > > +	}
> > > > > > 
> > > > > > Could you add a macro that assigns the value to the variable (or a struct
> > > > > > field in this case) when the read is successful? Add the print if you think
> > > > > > you need it.
> > > > > 
> > > > > I don't get this comment.
> > > > > Can you explain me better your plan please.
> > > > 
> > > > You have exactly the same pattern repeated over and over in a number of
> > > > functions. I'd like you to add a macro (or a function) that takes what
> > > > varies as arguments, and call that function here. It would reduce a lot of
> > > > the repeated lines code here.
> > > > 
> > > > ...
> > > 
> > > The best option is to print an error message in alvium_read() and drop
> > > all error messages from the callers.
> > 
> > What about don't print anything? We already have prints that comes from
> > CCI API if some errors occurs. Laurent suggest me this into some
> > previous comments. Let me know.
> 
> We need to print something somewhere as silent failures are bad. The
> messages printed by the CCI helpers are good enough, so no need to print
> anything specific in the alvium driver.

Oooks I'll follow your way on v7, thanks Laurent.
My plan is to switch to the following implementation:


static int alvium_get_img_width_params(struct alvium_dev *alvium)
{
	struct device *dev = &alvium->i2c_client->dev;
	u64 val;
	int ret = 0;

	if (!alvium->bcrm_addr)
		return -EINVAL;

	alvium_read(alvium, REG_BCRM_IMG_WIDTH_MIN_R, &val, &ret);
	alvium->img_min_width = val;
	dev_dbg(dev, "Min img width: %d\n", alvium->img_min_width);

	alvium_read(alvium, REG_BCRM_IMG_WIDTH_MAX_R, &val, NULL);
	alvium->img_max_width = val;
	dev_dbg(dev, "Max img width: %d\n", alvium->img_max_width);

	alvium_read(alvium, REG_BCRM_IMG_WIDTH_INC_R, &val, &ret);
	alvium->img_inc_width = val;
	dev_dbg(dev, "img width increment: %d px\n", alvium->img_inc_width);

	return ret;
}

Like you suggest. :)
What do you think about?

Thanks again,
Tommaso


> 
> -- 
> Regards,
> 
> Laurent Pinchart