[lkml]   [2013]   [Dec]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] spi: tegra: avoid unsigned->signed->unsigned promotion
> On Fri, Nov 29, 2013 at 06:12:44PM +0100, Michal Nazarewicz wrote:
>> u8 type, which is unsigned, is promoted to int, which is singned, when
>> doing a binary shift. Then, on 64-bit machines, it is further promoted
>> to unsigned long which may lead to more significant half of the value
>> to be all ones. To avoid this, explicitly promote to an unsigned type.

On Fri, Nov 29 2013, Thierry Reding wrote:
> But I don't think there's a real issue here. Even on 64-bit platforms,
> writel() will only write 32-bit registers, and therefore discard the
> upper 32 bits.
> I think in general perhaps a more proper fix would be to use only u32
> instead of unsigned long for these cases, since then the problem goes
> away. u32 is also the type of the value used by writel() so it makes
> perfect sense to use it.

Yes, you're absolutely right. I dunno why I missed the fact it's used
in writel only. I'll prepare a new patch soon(ish).

Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +--<>--<>--ooO--(_)--Ooo--
[unhandled content-type:application/pgp-signature]
 \ /
  Last update: 2013-12-02 14:41    [W:0.092 / U:0.716 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site