linux-kernel - Re: [PATCH v2 2/3] media: imx-mipi-csis: Store the number of data

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <175792829662.11401.2553264927858948770@isaac-ThinkPad-T16-Gen-2>
Date: Mon, 15 Sep 2025 10:24:56 +0100
From: Isaac Scott <isaac.scott@...asonboard.com>
To: Frank Li <Frank.li@....com>, Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: rmfrfs@...il.com, martink@...teo.de, kernel@...i.sm, mchehab@...nel.org, shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com, linux-media@...r.kernel.org, imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, hverkuil@...nel.org, nicolas.dufresne@...labora.com, sakari.ailus@...ux.intel.com, tomi.valkeinen@...asonboard.com, jonas@...boo.se, dan.scally+renesas@...asonboard.com, m.szyprowski@...sung.com, mehdi.djait@...ux.intel.com, niklas.soderlund+renesas@...natech.se
Subject: Re: [PATCH v2 2/3] media: imx-mipi-csis: Store the number of data_lanes configured in dt

Hi all,

Thank you very much for the reviews!

Quoting Laurent Pinchart (2025-09-04 16:01:53)
> On Wed, Sep 03, 2025 at 11:33:15AM -0400, Frank Li wrote:
> > On Wed, Sep 03, 2025 at 11:22:41AM +0100, Isaac Scott wrote:
> > > The number of lanes actively used by a MIPI CSI transmitter may differ
> > > from that which is defined in device tree. To allow us to be able to set
> > > the number of configured lanes without changing the maximum lane count,
> > > store the number of lanes configured in device tree, and adjust the
> > > debug print to reflect the device tree value.
> > >
> > > Signed-off-by: Isaac Scott <isaac.scott@...asonboard.com>
> > > ---
> > >  drivers/media/platform/nxp/imx-mipi-csis.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/media/platform/nxp/imx-mipi-csis.c b/drivers/media/platform/nxp/imx-mipi-csis.c
> > > index 2beb5f43c2c0..fc89325f2f94 100644
> > > --- a/drivers/media/platform/nxp/imx-mipi-csis.c
> > > +++ b/drivers/media/platform/nxp/imx-mipi-csis.c
> > > @@ -313,6 +313,8 @@ struct mipi_csis_device {
> > >     u32 hs_settle;
> > >     u32 clk_settle;
> > >
> > > +   unsigned int max_data_lanes;
> > > +
> > 
> > is num_data_lanes better? you get from vep.bus.mipi_csi2.num_data_lanes
> 
> That's a good point, but I think I prefer max_data_lanes here as it
> conveys better the fact that the field stores the maximum number of data
> lanes that can be used, not the number of data lanes being used at a
> given point of time.
> 
> This being said, why do we need this ? The maximum number of data lanes
> can be accessed through csis->bus.num_data_lanes. I've looked at patch
> 3/3 to answer this question, it there csis->bus.num_data_lanes is
> modified to store the number of data lanes used at runtime. I think it
> would be better to consider csis->bus as immutable after probe, and
> store the number of used data lanes in csis->num_data_lanes.

Yes, this makes a lot of sense. I only used max_data_lanes because I
wanted to avoid potential confusion between csis->bus.num_data_lanes and
csis->num_data_lanes; if that's not acutally an issue, I'll change it to
num_data_lanes.

> 
> Isaac, could you replace this patch by another one that adds
> csis->num_data_lanes, sets it to csis->bus.num_data_lanes in
> mipi_csis_async_register(), and replace usage of
> csis->bus.num_data_lanes with csis->num_data_lanes through the driver ?
> Patch 3/3 should then modify csis->num_data_lanes, not
> csis->bus.num_data_lanes.
> 

Good idea! Thanks, I'll take a look at submitting a v3.

Best wishes,

Isaac

> > >     spinlock_t slock;       /* Protect events */
> > >     struct mipi_csis_event events[MIPI_CSIS_NUM_EVENTS];
> > >     struct dentry *debugfs_root;
> > > @@ -1299,8 +1301,9 @@ static int mipi_csis_async_register(struct mipi_csis_device *csis)
> > >     }
> > >
> > >     csis->bus = vep.bus.mipi_csi2;
> > > +   csis->max_data_lanes = vep.bus.mipi_csi2.num_data_lanes;
> > >
> > > -   dev_dbg(csis->dev, "data lanes: %d\n", csis->bus.num_data_lanes);
> > > +   dev_dbg(csis->dev, "data lanes: %d\n", csis->max_data_lanes);
> > >     dev_dbg(csis->dev, "flags: 0x%08x\n", csis->bus.flags);
> > >
> > >     asd = v4l2_async_nf_add_fwnode_remote(&csis->notifier, ep,
> 
> -- 
> Regards,
> 
> Laurent Pinchart