On 10/02/18 13:07, H. Peter Anvin wrote: > Hi Johan et al, > > I'm trying to figure out what the status is of BOTHER and termios2 is in > various architectures, and I saw these patches: > > 1cee38f0363a88db374e50b232ca17b9a4c12fa0 > fefe287e4bf6ee23a5d9422a0a49de5389acc712 > > As you might know glibc never implemented this stuff, and I'm trying to fix > that. One of their questions is whether there are architectures on which > capability does *NOT* exist at this point. > > If you could help straighten this out it would be great. > > Specifically, are there any platforms: > > 1. where simply stuffing values into c_ispeed or c_ospeed and setting BOTHER > can be used to set the baud rate, even for the "standard" baud rates > (obviously breaking if the kernel is too old -- how old is that?) > > 2. where c_ispeed and c_ospeed aren't set, even if the value in c_cflags isn't > BOTHER? > > 3. > > Also: > > 4. I note alpha -- apparently as the only architecture -- doesn't define > BOTHER, even though it has B* constants that aren't the same as the > corresponding baud rates. It does, however, have c_[io]speed in its > legacy struct termios. Do you happen to know how this > is supposed to work on Alpha? There are claims that Alpha doesn't need it, > yet I see absolutely no support code for actually setting arbitary > > In fact, as far as I can tell, we could actually end up overrunning the > baud_table[] array on Alpha, as the limit check is only done on cbaud & > CBAUDEX, and CBAUDEX on Alpha is zero, yet Alpha has 32 possible values for > c_cflags & CBAUD, and the array is only 31 entries long. > > Should we just > > #define BOTHER 037 > > on Alpha, which ought to solve both problems, or is there a solution that > works even on legacy kernels? > > On a final note, <uapi/asm/termbits.h> isn't usable in building a libc, since > it pollutes the namespace. I would like to propose: > > a. Break out the constants into a separate uapi file; > b. Rename the exported structures __kernel_termios, __kernel_termios2 etc, > for the users which have explicit ioctls and need these structures. > This is a common problem in the headers, which bites extra hard with > names that are tags and not typedefs. The only real solution is to use > a very hidden namespace like __kernel_ and use #define if needed. > c. [Optionally] use an #ifdef to add these defines or, perhaps better for > legacy users, *not* define them. Alternatively a libc that doesn't want > them could #undef them. > Ping on this? I'm getting traction withe the glibc people and I want to nail this down as soon as possible. -hpa
