[Public] I seem to recall -ENOTSUPP being frowned upon for IOCTLs.
Alex From: McRae, Geoffrey <geoffrey.mc...@amd.com> Sent: Tuesday, July 8, 2025 5:13 AM To: Koenig, Christian <christian.koe...@amd.com>; Kuehling, Felix <felix.kuehl...@amd.com> Cc: Deucher, Alexander <alexander.deuc...@amd.com>; amd-gfx@lists.freedesktop.org; dri-de...@lists.freedesktop.org Subject: Re: [PATCH v2 1/1] drm/amdkfd: return -ENOTTY for unsupported IOCTLs [AMD Official Use Only - AMD Internal Distribution Only] I am happy to use EOPNOTSUPP but I must point out that this is not the pattern used across the kernel, the standard is to use ENOTTY, which is also the default that fs/ioctl.c returns when no handler is present. Userspace tooling such as strace and glibc specifically expectect ENOTTY to indicate invalid or unsupported IOCTL. ________________________________ From: Koenig, Christian <christian.koe...@amd.com<mailto:christian.koe...@amd.com>> Sent: Tuesday, 8 July 2025 5:01 PM To: McRae, Geoffrey <geoffrey.mc...@amd.com<mailto:geoffrey.mc...@amd.com>>; Kuehling, Felix <felix.kuehl...@amd.com<mailto:felix.kuehl...@amd.com>> Cc: Deucher, Alexander <alexander.deuc...@amd.com<mailto:alexander.deuc...@amd.com>>; amd-gfx@lists.freedesktop.org<mailto:amd-gfx@lists.freedesktop.org> <amd-gfx@lists.freedesktop.org<mailto:amd-gfx@lists.freedesktop.org>>; dri-de...@lists.freedesktop.org<mailto:dri-de...@lists.freedesktop.org> <dri-de...@lists.freedesktop.org<mailto:dri-de...@lists.freedesktop.org>> Subject: Re: [PATCH v2 1/1] drm/amdkfd: return -ENOTTY for unsupported IOCTLs On 08.07.25 06:22, Geoffrey McRae wrote: > Some kfd ioctls may not be available depending on the kernel version the > user is running, as such we need to report -ENOTTY so userland can > determine the cause of the ioctl failure. In general sounds like a good idea, but ENOTTY is potentially a bit misleading. We usually use EOPNOTSUPP for that even if its not the original meaning of that error code. Regards, Christian. > > Signed-off-by: Geoffrey McRae > <geoffrey.mc...@amd.com<mailto:geoffrey.mc...@amd.com>> > --- > drivers/gpu/drm/amd/amdkfd/kfd_chardev.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c > b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c > index a2149afa5803..36396b7318e7 100644 > --- a/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_chardev.c > @@ -3253,8 +3253,10 @@ static long kfd_ioctl(struct file *filep, unsigned int > cmd, unsigned long arg) > int retcode = -EINVAL; > bool ptrace_attached = false; > > - if (nr >= AMDKFD_CORE_IOCTL_COUNT) > + if (nr >= AMDKFD_CORE_IOCTL_COUNT) { > + retcode = -ENOTTY; > goto err_i1; > + } > > if ((nr >= AMDKFD_COMMAND_START) && (nr < AMDKFD_COMMAND_END)) { > u32 amdkfd_size; > @@ -3267,8 +3269,10 @@ static long kfd_ioctl(struct file *filep, unsigned int > cmd, unsigned long arg) > asize = amdkfd_size; > > cmd = ioctl->cmd; > - } else > + } else { > + retcode = -ENOTTY; > goto err_i1; > + } > > dev_dbg(kfd_device, "ioctl cmd 0x%x (#0x%x), arg 0x%lx\n", cmd, nr, > arg); >
