Hi Vegard, Le mardi 09 janvier 2024 à 14:08 +0100, Vegard Nossum a écrit : > On 08/01/2024 13:00, Paul Cercueil wrote: > > Add documentation for the three ioctls used to attach or detach > > externally-created DMABUFs, and to request transfers from/to > > previously > > attached DMABUFs. > > > > Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx> > > > > --- > > v3: New patch > > --- > > Documentation/usb/functionfs.rst | 36 > > ++++++++++++++++++++++++++++++++ > > 1 file changed, 36 insertions(+) > > Hi, > > I'd like to point out that this file (usb/functionfs.rst) is > currently > included by Documentation/subsystem-apis.rst, the top-level file for > the > "Kernel subsystem documentation" set of books, which describe > internal > APIs: "These books get into the details of how specific kernel > subsystems work from the point of view of a kernel developer". > > However, functionfs.rst (and especially your new additions) are > documenting a userspace API, so it really belongs somewhere in > Documentation/userspace-api/ -- that's where /proc, /sys, /dev and > ioctl > descriptions for userspace programmers belong. Agreed. Even the original content prior to my additions describe a userspace API. > > I'm not NAKing the patch -- I just want to draw attention to this > discrepancy. Maybe we can separate the kernel-implementation details > (stuff about __init sections and stuff) from the new ioctl() info? > > Looking at <https://docs.kernel.org/usb/> I see that there are many > other adjacent documents that are also not really documenting kernel > implementation details, rough categorization as follows: > > USB support > ----------- > > - Linux ACM driver v0.16 ==> admin/user info > - Authorizing (or not) your USB devices to connect to the system ==> > admin/user info > - ChipIdea Highspeed Dual Role Controller Driver => admin/user info > - DWC3 driver ==> driver TODOs (can be moved into source code?) > - EHCI driver ==> technical info + driver details > - How FunctionFS works > - Linux USB gadget configured through configfs ==> userspace API + > implementation > - Linux USB HID gadget driver ==> implementation + userspace API > - Multifunction Composite Gadget ==> technical + user info > - Linux USB Printer Gadget Driver ==> userspace API > - Linux Gadget Serial Driver v2.0 ==> user/admin + userspace API > - Linux UVC Gadget Driver ==> user/admin + userspace API > - Gadget Testing ==> user/admin + userspace API > - Infinity Usb Unlimited Readme ==> user/admin > - Mass Storage Gadget (MSG) ==> user/admin > - USB 7-Segment Numeric Display ==> user/admin > - mtouchusb driver ==> user/admin > - OHCI ==> technical info > - USB Raw Gadget ==> userspace API > - USB/IP protocol ==> technical info > - usbmon ==> user/admin + userspace API > - USB serial ==> user/admin + technical info > - USB references > - Linux CDC ACM inf > - Linux inf > - USB devfs drop permissions source > - Credits > > By "admin/user info", I mean things that a user would have to do or > run > (e.g. modprobe + flags) to make use of a driver; "technical info" is > more like device specifications (transfer speeds, modes of operation, > etc.); "userspace API" is stuff like configfs and ioctls; "driver > details" is really implementation details and internal > considerations. > > The last ones I don't even really know how to categorize. > > I'm guessing nobody is really enthralled by the idea of splitting > Documentation/usb/ up like this? > > Documentation/admin-guide/usb/ > Documentation/driver-api/usb/ (this one actually exists already) > Documentation/userspace-api/usb/ > > For the stuff that is _actually_ internal to a specific driver (so > not > useful for end users, not useful for admins, not generic USB info, > and > not useful for userspace programmers), I would honestly propose to > just > move it directly into the driver's source code, or, if the text is > obsolete, just get rid of it completely. > > The distinction between user/admin and userspace API is pretty clear > (one is for end users, the other is for userspace _programmers_), but > it > can sometimes be hard to determine whether something falls in one or > the > other category. > > In any case -- it looks like almost all of the usb/ directory does > not > document "how specific kernel subsystems work from the point of view > of > a kernel developer" so maybe we should just move the include to > userspace-api/ for now as an obvious improvement (if still not 100% > correct): > > diff --git a/Documentation/subsystem-apis.rst > b/Documentation/subsystem-apis.rst > index 2d353fb8ea26..fe972f57bf4c 100644 > --- a/Documentation/subsystem-apis.rst > +++ b/Documentation/subsystem-apis.rst > @@ -81,7 +81,6 @@ Storage interfaces > security/index > crypto/index > bpf/index > - usb/index > PCI/index > misc-devices/index > peci/index > diff --git a/Documentation/userspace-api/index.rst > b/Documentation/userspace-api/index.rst > index 82f9dbd228f5..e60cd9174ada 100644 > --- a/Documentation/userspace-api/index.rst > +++ b/Documentation/userspace-api/index.rst > @@ -41,6 +41,7 @@ Subsystem-specific documentation: > tee > isapnp > dcdbas > + ../usb/index > > Kernel ABIs: These documents describe the the ABI between the Linux > kernel and userspace, and the relative stability of these > interfaces. > > > Thoughts? Makes sense to me. There's definitely some cleanup to be done in the USB documentation. > Vegard Cheers, -Paul
