On Wed, 2017-08-30 at 12:50 +0200, Hannes Reinecke wrote:
> On 08/29/2017 06:02 PM, Bart Van Assche wrote:
> > On Tue, 2017-08-29 at 10:49 +0200, Hannes Reinecke wrote:
> > > +} sdev_bflags[] = {
> > > +#include "scsi_devinfo_tbl.c"
> > > +};
> > > +
> > > +static const char *sdev_bflags_name(unsigned int bflags)
> > > +{
> > > + int i;
> > > + const char *name = NULL;
> > > +
> > > + for (i = 0; i < ARRAY_SIZE(sdev_bflags); i++) {
> > > + if (sdev_bflags[i].value == bflags) {
> > > + name = sdev_bflags[i].name;
> > > + break;
> > > + }
> > > + }
> > > + return name;
> > > +}
> >
> > How about using ilog2() of the BLIST_* values as index of the table such that
> > an array lookup can be used instead of a for-loop over the entire array?
>
> Not sure if that'll work. The BLIST_* values in fact form a sparse
> array, so the lookup array 'sdev_bflags' actually an associative array.
> And I dare not convert it to a normal array as then I couldn't to the
> automatice table creation anymore.
>
> So I'm not sure if ilog2 will save me anything here.
Hello Hannes,
Are you aware that there is already code upstream for converting a bitmask
into a list of names of flags that supports sparse bit definitions? From
block/blk-mq-debugfs.c:
#define HCTX_FLAG_NAME(name) [ilog2(BLK_MQ_F_##name)] = #name
static const char *const hctx_flag_name[] = {
HCTX_FLAG_NAME(SHOULD_MERGE),
HCTX_FLAG_NAME(TAG_SHARED),
HCTX_FLAG_NAME(SG_MERGE),
HCTX_FLAG_NAME(BLOCKING),
HCTX_FLAG_NAME(NO_SCHED),
};
#undef HCTX_FLAG_NAME
static int blk_flags_show(struct seq_file *m, const unsigned long flags,
const char *const *flag_name, int flag_name_count)
{
bool sep = false;
int i;
for (i = 0; i < sizeof(flags) * BITS_PER_BYTE; i++) {
if (!(flags & BIT(i)))
continue;
if (sep)
seq_puts(m, "|");
sep = true;
if (i < flag_name_count && flag_name[i])
seq_puts(m, flag_name[i]);
else
seq_printf(m, "%d", i);
}
return 0;
}
[ ... ]
blk_flags_show(m, hctx->flags ^ BLK_ALLOC_POLICY_TO_MQ_FLAG(alloc_policy),
hctx_flag_name, ARRAY_SIZE(hctx_flag_name));
[ ... ]
Bart.
