From: Alexey Dobriyan <email@example.com> To: James Bottomley <James.Bottomley@HansenPartnership.com> Cc: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org Subject: Re: [PATCH] unaligned: delete 1-byte accessors Date: Mon, 22 Jul 2019 09:07:44 +0300 [thread overview] Message-ID: <20190722060744.GA24253@avx2> (raw) In-Reply-To: <1563774526.3223.2.camel@HansenPartnership.com> On Mon, Jul 22, 2019 at 02:48:46PM +0900, James Bottomley wrote: > On Mon, 2019-07-22 at 08:22 +0300, Alexey Dobriyan wrote: > > On Mon, Jul 22, 2019 at 08:08:33AM +0900, James Bottomley wrote: > > > On Mon, 2019-07-22 at 00:52 +0300, Alexey Dobriyan wrote: > > > > Each and every 1-byte access is aligned! > > > > > > The design idea of this is for parsing descriptors. We simply > > > chunk up the describing structure using get_unaligned for > > > everything. The reason is because a lot of these structures come > > > with reserved areas which we may make use of later. If we're using > > > get_unaligned for everything we can simply change a u8 to a u16 in > > > the structure absorbing the reserved padding. With your change now > > > I'd have to chase down every byte access and replace it with > > > get_unaligned instead of simply changing the structure. > > > > > > What's the significant advantage of this change that compensates > > > for the problems the above causes? > > > > HW descriptors have fixed endianness, you're supposed to use > > get_unaligned_be32() and friends. > > Not if this is an internal descriptor format, which is what this is > mostly used for. Maybe, but developer is supposed to look at all struct member usages while changing types, right? > > For that matter, drivers/scsi/ has exactly 2 get_unaligned() calls > > one of which can be changed to get_unaligned_be32(). > > You haven't answered the "what is the benefit of this change" question. > I mean sure we can do it, but it won't make anything more efficient > and it does help with the descriptor format to treat every structure > field the same. The benefit is less code, come on. Another benefit is that typoing get_unaligned((u16*)p) for get_unaligned((u8*)p) will get detected.
next prev parent reply other threads:[~2019-07-22 6:07 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-07-21 21:52 Alexey Dobriyan 2019-07-21 23:08 ` James Bottomley 2019-07-22 5:22 ` Alexey Dobriyan 2019-07-22 5:48 ` James Bottomley 2019-07-22 6:07 ` Alexey Dobriyan [this message] 2019-07-22 6:20 ` James Bottomley
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