On Mon, Apr 27, 2015 at 3:35 PM, James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: > On Mon, 2015-04-27 at 14:59 -0700, Andy Lutomirski wrote: >> On Fri, Apr 24, 2015 at 8:16 AM, James Bottomley >> <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote: >> > On Fri, 2015-04-24 at 02:14 +0000, Kweh, Hock Leong wrote: >> >> > -----Original Message----- >> >> > From: James Bottomley [mailto:James.Bottomley@xxxxxxxxxxxxxxxxxxxxx] >> >> > Sent: Thursday, April 23, 2015 10:10 PM >> >> > >> >> > On Thu, 2015-04-23 at 08:30 +0000, Kweh, Hock Leong wrote: >> >> > > > -----Original Message----- >> >> > > > From: James Bottomley >> >> > [mailto:James.Bottomley@xxxxxxxxxxxxxxxxxxxxx] >> >> > > > Sent: Wednesday, April 22, 2015 11:19 PM >> >> > > > >> >> > > > >> >> > > > Yes, I think we've all agreed we can do it ... it's now a question of whether >> >> > we >> >> > > > can stomach the ick factor of actually initiating a transaction in close ... I'm >> >> > still >> >> > > > feeling queasy. >> >> > > >> >> > > The file "close" here can I understand that the file system will call the >> >> > "release" >> >> > > function at the file_operations struct? >> >> > > http://lxr.free-electrons.com/source/include/linux/fs.h#L1538 >> >> > > >> >> > > So, James you are meaning that we could initiating the update transaction >> >> > > inside the f_ops->release() and return the error code if update failed in this >> >> > > function? >> >> > >> >> > Well, that's what I was thinking. However the return value of ->release >> >> > doesn't get propagated in sys_close (or indeed anywhere ... no idea why >> >> > it returns an int) thanks to the task work additions, so we'd actually >> >> > have to use the operation whose value is propagated in sys_close() which >> >> > turns out to be flush. >> >> > >> >> > James >> >> > >> >> >> >> Okay, I think I got you. Just to double check for in case: you are meaning >> >> to implement it at f_ops->flush() instead of f_ops->release(). >> > >> > Well, what I'm saying is that the only way to propagate an error to >> > close is by returning one from the flush file_operation. >> > >> > Let's cc fsdevel to see if they have any brighter ideas. >> > >> > The problem is we need to update firmware (several megabytes of it) via >> > standard system tools. We're thinking cat to a device. The problem is >> > that we need an error code back once the update goes through (which it >> > can't until we've fed all the firmware data into the system). To use >> > standard unix tools, we have to trigger off the standard system calls >> > cat uses and since write() will happen in chunks, the only way to commit >> > the transaction is in close(). >> > >> > We initially through of initiating the transaction in f_ops->release and >> > returning the error code there, but that doesn't work because its value >> > isn't actually propagated, so we're now thinking of initiating the >> > transaction in f_ops->flush instead (this is a device, not a file, so it >> > won't get any other flushers). Are there any other ways for us to >> > propagate error on close? >> > >> >> I think we may end up wanting to support both UpdateCapsule and >> QueryCapsuleCapabilities, in which case this gets awkward. Maybe we >> really should do a misc device + ioctl. > > To be honest, I hate ioctls ... especially the "have to use special > tools" part. > > Would we ever want to support QueryCapsuleUpdate()? The return codes on > error are the same as UpdateCapsule() but the query call does nothing on > success (and the update call updates, obviously), so it seems a bit > pointless if someone's gone to the trouble of getting a capsule ... they > obviously want to apply it rather than know if it could be applied. I can imagine a UI that would try to validate a transaction consisting of several of these things, tell the user whether it'll work and whether a reboot is needed, and then do it. > > Assuming we do, we could just use the same error on close mechanism, but > use sysfs binary attributes ... or probably something new like a binary > transaction attribute that does all the transaction on close magic for > us. Yeah, but now we have both input and output, so as ugly as ioctl is, it's a pretty good match. Sigh. This is all more complicated than it deserves to me. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
