On Mon, Nov 3, 2014 at 10:04 PM, Kweh, Hock Leong <hock.leong.kweh@xxxxxxxxx> wrote: >> -----Original Message----- >> From: Andy Lutomirski [mailto:luto@xxxxxxxxxxxxxx] >> > >> > Andy, here's the steps to load a capsule. I don't have a problem with >> > this, it's userspace driven, no "autoloading" of files in /lib/, and >> > works with sysfs. >> > >> > Have any objection to it, I don't. > > Thanks Greg for helping me on the explanation. I would like to apologize if > my cover letter/commit messages did misleading. > >> >> After reading the code, I still have objections. >> >> The full workflow seems to be, from the user's POV: >> >> 1. load the module >> >> 2. hope that there isn't a file called /lib/firmware/efi-capsule-file >> >> 3. echo 1 >.../loading >> >> 4. cat firmware >.../data >> >> 5. echo 0 >.../loading >> >> 6. efi_update_capsule gets called. The return value ends up in the kernel >> logs somewhere but doesn't seem to make it to userspace. >> >> 7. reboot(), but only if the capsule you loaded requires a reboot, which may >> or may not be detectable without the kernel's help (I'm not sure about this >> point). >> >> If you want to load a second capsule (which seems like a reasonable thing to >> do if the first capsule was the kind that is processed immediately), then >> rmmod -f the module and start over? > > You no need to do rmmod in order to upload the 2nd capsule binary. You just need to > do the 3 steps as you mentioned in your 3, 4 and 5 for your 2nd or 3rd capsule binaries. > Then the last, you do the reboot. OK. I missed that you request firmware again after each request finishes. > >> >> This seems like an unpleasant interface. I think that ioctl or a dedicated >> custom sysfs file would be considerably nicer. It would allow you to upload a >> capsule and get an indication of success or failure all at once, and it lets you >> load more than one capsule. >> Also, it gets rid of some of the really weird module refcounting stuff that's >> going on -- the only unusual thing the module would do would be to pin itself >> once a reboot-requiring capsule is loaded. >> >> --Andy >> > > Regarding the synchronization, it is only required for module unload. The code is designed > in such a way that allow to be built as a kernel module or built into the kernel. If you choose > the built in kernel method, you won't come into the module unload situation which require > the synchronization. > It seems like a large fraction of the code in this module exists just to work around the fact that request_firmware doesn't do what you want it to do. You have code to: - Prevent the /lib/firmware mechanism from working. - Avoid a deadlock by doing strange things in the unload code. - Allow more than one capsule per module load. (Isn't this hard to use? User code will have to wait for the next firmware request before sending a second capsule.) All of this is for dubious gain. You have to do three separate opens in sysfs to upload a capsule, and there's no way to report back to userspace whether the EFI call worked and whether a reboot is needed. What's the benefit of using the firmware interface here? --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
