[PATCH v2 1/3] staging: vc04_services: Support module autoloading using MODULE_DEVICE_TABLE

[Laurent Pinchart]

On Wed, Oct 18, 2023 at 11:12:12AM +0530, Umang Jain wrote:
> VC04 has now a independent bus vchiq_bus to register its devices.
> However, the module auto-loading for bcm2835-audio and bcm2835-camera
> currently happens through MODULE_ALIAS() macro specified explicitly.
> 
> The correct way to auto-load a module, is when the alias is picked
> out from MODULE_DEVICE_TABLE(). In order to get there, we need to
> introduce  vchiq_device_id and add relevant entries in file2alias.c
> infrastructure so that aliases can be generated. This patch targets
> adding vchiq_bus_device_id and do_vchiq_bus_entry, in order to
> generate those alias using the /script/mod/file2alias.c.
> 
> Going forward the MODULE_ALIAS() from bcm2835-camera and bcm2835-audio
> will be dropped, in favour of MODULE_DEVICE_TABLE being used there.
> 
> The alias format for vchiq_bus devices will be "vchiq_bus:<dev_name>".
> Adjust the vchiq_bus_uevent() to reflect that.

None of the other buses have a "_bus" suffix in the alias or in the
*_device_id structure name. Is there a reason to make an exception here?

> Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
> ---
>  .../vc04_services/interface/vchiq_arm/vchiq_bus.c        | 2 +-
>  .../vc04_services/interface/vchiq_arm/vchiq_bus.h        | 3 +++
>  include/linux/mod_devicetable.h                          | 4 ++++
>  scripts/mod/devicetable-offsets.c                        | 3 +++
>  scripts/mod/file2alias.c                                 | 9 +++++++++
>  5 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_bus.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_bus.c
> index 4ac3491efe45..b4915bd76387 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_bus.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_bus.c
> @@ -26,7 +26,7 @@ static int vchiq_bus_uevent(const struct device *dev, struct kobj_uevent_env *en
>  {
>  	const struct vchiq_device *device = container_of_const(dev, struct vchiq_device, dev);
>  
> -	return add_uevent_var(env, "MODALIAS=%s", dev_name(&device->dev));
> +	return add_uevent_var(env, "MODALIAS=vchiq_bus:%s", dev_name(&device->dev));
>  }
>  
>  static int vchiq_bus_probe(struct device *dev)
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_bus.h b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_bus.h
> index 7eaaf9a91cda..6e1fbee4b078 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_bus.h
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_bus.h
> @@ -7,6 +7,7 @@
>  #define _VCHIQ_DEVICE_H
>  
>  #include <linux/device.h>
> +#include <linux/mod_devicetable.h>
>  
>  struct vchiq_device {
>  	struct device dev;
> @@ -18,6 +19,8 @@ struct vchiq_driver {
>  	int		(*resume)(struct vchiq_device *device);
>  	int		(*suspend)(struct vchiq_device *device,
>  				   pm_message_t state);
> +
> +	const struct vchiq_bus_device_id *id_table;
>  	struct device_driver driver;
>  };
>  
> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> index b0678b093cb2..f01e175f7f3d 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -946,4 +946,8 @@ struct cdx_device_id {
>  	__u32 override_only;
>  };
>  
> +struct vchiq_bus_device_id {
> +	char name[32];
> +};
> +
>  #endif /* LINUX_MOD_DEVICETABLE_H */
> diff --git a/scripts/mod/devicetable-offsets.c b/scripts/mod/devicetable-offsets.c
> index abe65f8968dd..c9a02d2c4f9e 100644
> --- a/scripts/mod/devicetable-offsets.c
> +++ b/scripts/mod/devicetable-offsets.c
> @@ -267,5 +267,8 @@ int main(void)
>  	DEVID_FIELD(cdx_device_id, device);
>  	DEVID_FIELD(cdx_device_id, override_only);
>  
> +	DEVID(vchiq_bus_device_id);
> +	DEVID_FIELD(vchiq_bus_device_id, name);
> +
>  	return 0;
>  }
> diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
> index 38120f932b0d..6908dc70b649 100644
> --- a/scripts/mod/file2alias.c
> +++ b/scripts/mod/file2alias.c
> @@ -1478,6 +1478,14 @@ static int do_cdx_entry(const char *filename, void *symval,
>  	return 1;
>  }
>  
> +static int do_vchiq_bus_entry(const char *filename, void *symval, char *alias)
> +{
> +	DEF_FIELD_ADDR(symval, vchiq_bus_device_id, name);
> +	sprintf(alias, "vchiq_bus:%s", *name);
> +
> +	return 1;
> +}
> +
>  /* Does namelen bytes of name exactly match the symbol? */
>  static bool sym_is(const char *name, unsigned namelen, const char *symbol)
>  {
> @@ -1558,6 +1566,7 @@ static const struct devtable devtable[] = {
>  	{"dfl", SIZE_dfl_device_id, do_dfl_entry},
>  	{"ishtp", SIZE_ishtp_device_id, do_ishtp_entry},
>  	{"cdx", SIZE_cdx_device_id, do_cdx_entry},
> +	{"vchiq_bus", SIZE_vchiq_bus_device_id, do_vchiq_bus_entry},
>  };
>  
>  /* Create MODULE_ALIAS() statements.

-- 
Regards,

Laurent Pinchart