Am 11.10.2017 um 21:36 schrieb Mauro Carvalho Chehab:
> changeset 6bbf7a855d20 ("media: dvbdev: convert DVB device types into an enum")
> added a new warning on gcc 6:
>
>>> drivers/media/dvb-core/dvbdev.c:86:1: warning: control reaches end of non-void function [-Wreturn-type]
>
> That's because gcc is not smart enough to see that all types are
> present at the switch. Also, the current code is not too optimized.
>
How should the compiler know that "int type" will only contain values
0..8? dvb_register_adapter is not inlined.
> So, replace it to a more optimized one, based on a static table.
>
> Reported-by: kbuild test robot <fengguang.wu@xxxxxxxxx>
> Fixes: 6bbf7a855d20 ("media: dvbdev: convert DVB device types into an enum")
> Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxxxxxxxx>
> ---
> I actually suggested this patch to be fold with changeset 6bbf7a855d20.
> Unfortunately, I actually forgot to do that (I guess I did, but on a different
> machine than the one I used today to pick it).
>
> Anyway, that saves some code space with static minors and cleans up
> a warning. So, let's apply it.
>
> drivers/media/dvb-core/dvbdev.c | 28 +++++++++++++---------------
> 1 file changed, 13 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c
> index a53eb53a4fd5..060c60ddfcc3 100644
> --- a/drivers/media/dvb-core/dvbdev.c
> +++ b/drivers/media/dvb-core/dvbdev.c
> @@ -68,22 +68,20 @@ static const char * const dnames[] = {
> #else
> #define DVB_MAX_IDS 4
>
> -static int nums2minor(int num, enum dvb_device_type type, int id)
> -{
> - int n = (num << 6) | (id << 4);
> +static const u8 minor_type[] = {
> + [DVB_DEVICE_VIDEO] = 0,
> + [DVB_DEVICE_AUDIO] = 1,
> + [DVB_DEVICE_SEC] = 2,
> + [DVB_DEVICE_FRONTEND] = 3,
> + [DVB_DEVICE_DEMUX] = 4,
> + [DVB_DEVICE_DVR] = 5,
> + [DVB_DEVICE_CA] = 6,
> + [DVB_DEVICE_NET] = 7,
> + [DVB_DEVICE_OSD] = 8,
> +};
>
> - switch (type) {
> - case DVB_DEVICE_VIDEO: return n;
> - case DVB_DEVICE_AUDIO: return n | 1;
> - case DVB_DEVICE_SEC: return n | 2;
> - case DVB_DEVICE_FRONTEND: return n | 3;
> - case DVB_DEVICE_DEMUX: return n | 4;
> - case DVB_DEVICE_DVR: return n | 5;
> - case DVB_DEVICE_CA: return n | 6;
> - case DVB_DEVICE_NET: return n | 7;
> - case DVB_DEVICE_OSD: return n | 8;
> - }
> -}
> +#define nums2minor(num, type, id) \
> + (((num) << 6) | ((id) << 4) | minor_type[type])
In this code it is problematic that a bad value of type will trigger an
invalid memory access.
>
> #define MAX_DVB_MINORS (DVB_MAX_ADAPTERS*64)
> #endif
>
Regards
Matthias
