Date: Wed, 27 Apr 2016 04:44:56 +0000 From: Jaydeep Patil <Jaydeep.Patil@...tec.com> To: Szabolcs Nagy <nsz@...t70.net>, "musl@...ts.openwall.com" <musl@...ts.openwall.com> Subject: RE: mips64/n32 struct termios >-----Original Message----- >From: Szabolcs Nagy [mailto:nsz@...t70.net] >Sent: 27 April 2016 AM 12:14 >To: musl@...ts.openwall.com >Cc: Jaydeep Patil >Subject: Re: [musl] mips64/n32 struct termios > >* Rich Felker <dalias@...c.org> [2016-04-26 13:27:04 -0400]: >> I noticed that the mips64/n32 versions of struct termios have omitted >> the two speed_t fields at the end, which other archs (including mips) >> all have. It's dubious whether these make sense or are useful for >> anything, and I don't even recall the whole history of why we have >> them, but as long as we do have them for all the other archs I kind of >> think it makes sense to put them back for mips64/n32 in case we ever >> need them for something (or for expansion) or want generic code to be >> able to access them. >> >> Was there a reason they were omitted in the new ports? Any objection >> to adding them back? > >see my [PATCH 16/16] fix struct termios in mips termios.h (that can be done in >the other direction fixing mips64,n32) > >termios struct is special on mips and ppc: > >mips glibc: NCCS = 32, no speed fields >mips linux: NCCS = 23 > >ppc glibc: NCCS = 32, speed fields >ppc linux: NCCS = 19, c_line swapped, only termios, no termios2 > >other glibc: NCCS = 32, speed fields >other linux: NCCS = 19 > >the kernel side only has speed fields in termios2 except on ppc where termios >has them, in glibc termios has speed fields except on mips. (the __ prefixed >fields are only present in musl probably to match the termios struct size on >x86.) > >i don't know why there are these differences and how it can work in practice, >but e.g. util-linux ldattach seems to use them with BOTHER cflag and probably >one can query them with TCGETS(2). > >glibc tcsetattr/tcgetattr translates glibc termios to kernel termios, so one can >set/get the fields that way too and there is further powerpc specific magic in >that translation. I don't see any significance/reference to input/output speed fields of the struct termios in mips linux/glibc. We can omit these fields. >> >> Rich
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