[CC'ed interested parties in retrospect and resent in plain text] On 11 March 2011 15:20, Andy Green <andy@xxxxxxxxxxx> wrote: > > Hi - > > platform_data is a well established way in Linux to pass configuration data up to on-board assets from a machine file like mach-xyz.c. It's also supported to pass platform_data up to devices that are probed asynchronously from busses like i2c as well, which is very handy. > > However AFAIK it's not possible to bind platform_data to probed USB devices as it stands. > > There are now boards which have on-board USB assets, for example OMAP4 Panda which has a USB <-> Ethernet bridge wired up permanently. It'd be convenient to also be able to pass optional platform_data to these devices when they are asynchronously probed. > > So what's the feeling about a new api to register an array of platform_data pointers bound to static "devpath" names in the machine file? > > When a usb device is instantiated, it can check through this array if it exists, matching on devname, and attach the platform_data to the underlying probed usb device's dev->platform_data, which it seems is currently unused. > > The particular use that suggested this is on Panda, it would be ideal to be able to set a flag in the usb device's platform data that forces it to be named eth%d since it's a hardwired asset on the board with an RJ45 socket. > > Comments, implementation suggestions, enquiries as to my level of crack consumption etc welcomed ^^ Hi Andy, Personally, I wouldn't have bothered thinking about some kernel-wide solution to the Panda SMSC9514 issue. I think defining Panda specific udev rules to 'rename the SMSC9614 on USB1(?) to ETH0' is sufficient and legal to do. Bus enumeration algos change neither often nor enough. I believe there would be far riskier assumptions in filesystems already. But I do agree it is nice to have system wide solutions whenever due. Like this attempted patchset. Which is based upon two questions :- Q(a) Can discoverable buses(USB, SDIO etc) legally need platform_data or similar? Q(b) If yes, what 'key' is most suitable for identifying the right device to attach the data to ? (a) We already have a good example, of Panda's missing MAC. I am sure there would be more to think of. Though it is illegal for a NIC to not have MAC address, no spec demands the MAC be on some EEPROM or like. Theoretically, the NIC vendor could hand me a NIC and a note with it's unique MAC address scribbled :) As Mark already noted, savings pile if we could save eeproms when a device is expected to ship in tens of thousands. IIANM, Greg acknowledged passing MAC via board specific data structure(albeit via DT) It's a different matter that DT has many hearts to win(at least in ARM Linux) So, perhaps the answer to Q(a) is - Yes. (b) IMHO, though stable enough, the most obvious method of 'devpath association' is indeed not future-proof. Having parent pointers to compare sounds like a bit too intrusive. People might want to suggest? Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
