[PATCH v7 1/2] module: add SCMI device table alias support

[Sudeep Holla]

On Wed, Sep 23, 2026 at 12:23:50PM +0200, Hans de Goede wrote:
> Hi,
> 
> On 23-Sep-26 11:07, Sudeep Holla wrote:
> > On Mon, Sep 21, 2026 at 05:19:45PM +0200, Uwe Kleine-König wrote:
> >> On Fri, Sep 18, 2026 at 11:29:50AM +0200, Hans de Goede wrote:
> >>> From: Bjorn Andersson <bjorn.andersson at oss.qualcomm.com>
> >>>
> >>> SCMI client drivers already describe their bus match data with
> >>> MODULE_DEVICE_TABLE(scmi, ...), but modpost does not know how to consume
> >>> SCMI device tables. As a result, SCMI modules do not get generated module
> >>> aliases from their id tables.
> >>>
> >>> Move struct scmi_device_id to mod_devicetable.h so it has a fixed layout
> >>> visible to modpost, add the corresponding generated offsets and teach
> >>> file2alias to emit scmi:<protocol>:<name> aliases.
> >>>
> >>> Use the same stable alias format for SCMI device uevents and sysfs
> >>> modaliases. The previous string included the instance-specific device
> >>> name, which is not useful for matching modules.
> >>>
> >>> Assisted-by: Codex:GPT-5.5
> >>> Reviewed-by: Hans de Goede <johannes.goede at oss.qualcomm.com>
> >>> Tested-by: Hans de Goede <johannes.goede at oss.qualcomm.com>
> >>> Signed-off-by: Bjorn Andersson <bjorn.andersson at oss.qualcomm.com>
> >>> Signed-off-by: Hans de Goede <johannes.goede at oss.qualcomm.com>
> > 
> > [...]
> > 
> >>> diff --git a/include/linux/device-id/scmi.h b/include/linux/device-id/scmi.h
> >>> new file mode 100644
> >>> index 000000000000..1b4ccfa9dcc5
> >>> --- /dev/null
> >>> +++ b/include/linux/device-id/scmi.h
> >>> @@ -0,0 +1,17 @@
> >>> +/* SPDX-License-Identifier: GPL-2.0-only */
> >>> +#ifndef LINUX_DEVICE_ID_SCMI_H
> >>> +#define LINUX_DEVICE_ID_SCMI_H
> >>> +
> >>> +#ifdef __KERNEL__
> >>> +#include <linux/types.h>
> >>> +#endif
> >>> +
> >>> +#define SCMI_NAME_SIZE		32
> >>> +#define SCMI_MODULE_PREFIX	"scmi:"
> >>> +
> >>> +struct scmi_device_id {
> >>> +	__u8 protocol_id;
> >>> +	char name[SCMI_NAME_SIZE];
> >>
> >> I wonder if you tried to keep this a char *. ISTR someone did something
> >> similar recently and they claimed it worked. That would get rid of the
> >> artificial name size limit and simplify this patch.
> >>
> > 
> > I agree with this. 
> 
> Ok, so I checked and no other include/linux/device-id/*.h file
> defines a foo_device_id field with a type of "char *" and
> then uses that field in scripts/mod/devicetable-offsets.c /
> scripts/mod/file2alias.c .
> 

I looked at hda_device_id and its uses. It looks like it does use
char * and there were loads of drivers initialising the string. I must
be missing something then ?

> 2 device-id/foo.h headers (dmi, pcmcia) do define a "char *"
> field, but then do NOT use that to generate a modalias.
> 
> So scmi_device_id would be the first to do this.
> 

Your response made me dig further and I found snd_hdac_codec_modalias()
which seems to do the magic there.

> Despite that I still gave this a try. Things do compile,
> but it results in a modalias for the scmi-cpufreq driver
> of: scmi:13:(null) and auto-loading unsurprisingly does
> not work.
> 

Fair enough, looking at snd_hdac_codec_modalias() it sounds right.

Uwe, do you think we need to follow something like snd_hdac_codec_modalias()
or this size limit is okay ?

-- 
Regards,
Sudeep