On 29/05/15 11:48, David Laight wrote:
> From: Shradha Shah
>> Sent: 29 May 2015 11:01
>> On every adapter there will be one primary PF per adaptor and
>> one link control PF per port.
> ...
>> + return sprintf(buf, "%d\n",
>> + ((efx->mcdi->fn_flags) &
>> + (1 << MC_CMD_DRV_ATTACH_EXT_OUT_FLAG_LINKCTRL))
>> + ? 1 : 0);
> Horrid expression.
> Why not:
> (efx->mcdi->fn_flags >> MC_CMD_DRV_ATTACH_EXT_OUT_FLAG_LINKCTRL) & 1
I think the idea is that this is more explicit about what it's doing.
It's a toss-up which is more readable / idiomatic; I prefer the OP version.
(They probably compile to the same thing, though I haven't checked.)
> using sprintf() is also excessive. Maybe:
> *buf = '0' + (expression);
> return 1;
That loses the '\n'; it's annoying when you cat a file and it doesn't end in a
'\n', because it gloms onto your shell prompt.
sprintf isn't really that expensive, this isn't likely to be called very
frequently.
> You may also need to check for buffer overrun.
In fact Documentation/filesystems/sysfs.txt says that "show() should always use
scnprintf()" and that "The buffer will always be PAGE_SIZE bytes in length."
So if we want to be consistent, it should be
return scnprintf(buf, PAGE_SIZE, "%d\n", expression);
although it'd be rather surprising if either 0\n or 1\n were ever too big for
PAGE_SIZE :grin:.
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