Re: [PATCH v3 14/14] greybus: cpc: add CPC SDIO host driver

["Jérôme Pouiller" <jerome.pouiller@silabs.com>]

Hello Damien,

On Thursday 12 February 2026 15:43:52 Central European Standard Time Damien Riégel wrote:
> From: Gabriel Beaulieu <gabriel.beaulieu@silabs.com>
> 
> This introduces a new module gb-cpc-sdio, in order to communicate with a
> Greybus CPC device over SDIO.
> 
> Most of the complexity stems from aggregation: packets are aggregated to
> minimize the number of CMD53s. In the first block, the first le32 is the
> number of packets in this transfer. Immediately after that are all the
> packet headers (CPC + Greybus). This lets the device process all the
> headers in a single interrupt, and prepare the ADMA descriptors for all
> the payloads in one go.
> 
> Payloads start at the beginning of the second block and are concatained.
> Their lengths must be 32-bit aligned, so the driver takes care of adding
> and removing padding if necessary.
> 
> Signed-off-by: Gabriel Beaulieu <gabriel.beaulieu@silabs.com>
> Signed-off-by: Damien Riégel <damien.riegel@silabs.com>
> ---
> Changes in v3:
>   - rework defines to group together address-related defines and remove
>     orphaned value
>   - remove trivial comments
>   - all RX and TX are now done from the workqueue. In previous
>     iterations, transfers could either be done from the threaded IRQ or
>     from the workqueue.
>   - remove erroneous SDIO VID/PID
>   - remove padding between headers and payloads when aggregating
> 
> Changes in v2:
>   - change formatting from %lu to %zu when printing size_t's
>   - remove "/**" kernel-doc marker for static functions not actually
>     using the kernel-doc format
>   - reduce header inclusion list
>   - use reverse christmas tree variable declarations consistently
>   - update aggregation functions to try to be more legible
>   - use define instead of constant value 0x0C for the address where to
>     read the number of bytes the device wants to send
> 
>  drivers/greybus/cpc/Kconfig  |  12 +
>  drivers/greybus/cpc/Makefile |   3 +
>  drivers/greybus/cpc/sdio.c   | 480 +++++++++++++++++++++++++++++++++++
>  3 files changed, 495 insertions(+)
>  create mode 100644 drivers/greybus/cpc/sdio.c
> 
[...]
> +static const struct sdio_device_id sdio_ids[] = {
> +	/* No official ID */
> +	{ SDIO_DEVICE(0x0000, 0x1000), },

Can you provide some details about how it's work? I assume Silabs sells
OEM products and each vendor has to set their own VID/PID, that's it?

I assume Silabs also has samples products. How it works for them? Is
there a default VID/PID or the sample firmware won't compile until the
user changes the VID/PID?

In any case, I believe we can't publish a driver with VID = 0.

(BTW, I suggest to include linux-mmc@vger.kernel.org as recipient of
this PR).

-- 
Jérôme Pouiller