On Tue, Nov 12, 2019 at 5:38 PM Takashi Iwai <tiwai@xxxxxxx> wrote:
> On Tue, 12 Nov 2019 16:16:39 +0100, Arnd Bergmann wrote:
> > +#ifndef __KERNEL__
> > struct snd_rawmidi_status {
> > int stream;
> > + unsigned char pad1[sizeof(time_t) - sizeof(int)];
> > struct timespec tstamp; /* Timestamp */
> > size_t avail; /* available bytes */
> > size_t xruns; /* count of overruns since last status (in bytes) */
> > unsigned char reserved[16]; /* reserved for future use */
> > };
>
> Can we use union instead of padding? Something like:
>
> struct snd_rawmidi_status {
> union {
> int stream;
> time_t stream_alignment;
> };
> struct timespec tstamp; /* Timestamp */
> ....
I think this would work most of the time, though I don't feel this is more
readable than the other version.
More importantly, it requires compiling user applications with GNU extensions
(--std=gnu89 or higher) or C11, but not C99, so this could be a problem
for some applications.
If you feel there is a problem with the padding syntax, how about enclosing
it in a typedef like:
typedef struct { char pad[sizeof(time_t) - sizeof(int)]; } __time_pad;
This typedef could be used in several structures from the other patches
as well.
Arnd
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