On Mon, Sep 9, 2013 at 6:33 PM, David Herrmann <dh.herrmann@xxxxxxxxx> wrote:
> udev has this nice feature of creating "dead" /dev/<node> device-nodes if
> it finds a devnode:<node> modalias. Once the node is accessed, the kernel
> automatically loads the module that provides the node. However, this
> requires udev to know the major:minor code to use for the node. This
> feature was introduced by:
>
> commit 578454ff7eab61d13a26b568f99a89a2c9edc881
> Author: Kay Sievers <kay.sievers@xxxxxxxx>
> Date: Thu May 20 18:07:20 2010 +0200
>
> driver core: add devname module aliases to allow module on-demand auto-loading
>
> However, uhid uses dynamic minor numbers so this doesn't actually work. We
> need to load uhid to know which minor it's going to use.
>
> Hence, allocate a static minor (just like uinput does) and we're good
> to go.
>
> Reported-by: Tom Gundersen <teg@xxxxxxx>
Thanks, this works (I only tested the creation of the device node, not
the actual module loading).
> Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxx>
> ---
> drivers/hid/uhid.c | 3 ++-
> include/linux/miscdevice.h | 1 +
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
> index 5bf2fb7..93b00d7 100644
> --- a/drivers/hid/uhid.c
> +++ b/drivers/hid/uhid.c
> @@ -615,7 +615,7 @@ static const struct file_operations uhid_fops = {
>
> static struct miscdevice uhid_misc = {
> .fops = &uhid_fops,
> - .minor = MISC_DYNAMIC_MINOR,
> + .minor = UHID_MINOR,
> .name = UHID_NAME,
> };
>
> @@ -634,4 +634,5 @@ module_exit(uhid_exit);
> MODULE_LICENSE("GPL");
> MODULE_AUTHOR("David Herrmann <dh.herrmann@xxxxxxxxx>");
> MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
> +MODULE_ALIAS_MISCDEV(UHID_MINOR);
> MODULE_ALIAS("devname:" UHID_NAME);
> diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h
> index 09c2300..cb35835 100644
> --- a/include/linux/miscdevice.h
> +++ b/include/linux/miscdevice.h
> @@ -45,6 +45,7 @@
> #define MAPPER_CTRL_MINOR 236
> #define LOOP_CTRL_MINOR 237
> #define VHOST_NET_MINOR 238
> +#define UHID_MINOR 239
> #define MISC_DYNAMIC_MINOR 255
>
> struct device;
> --
> 1.8.4
>
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