On Thursday 22 September 2016, Ard Biesheuvel wrote: > ================================================================================ > NOTE: this is a work in progress, and not fully functional yet. In particular, > the actual MMC host protocol methods are stubbed out at the moment, and need to > be wired up to the Linux device drivers. > ================================================================================ > > On mobile and embedded systems, there is usually only a single MMC device for > non-volatile storage, which sits behind a controller that is owned by the OS at > runtime. This makes it difficult to host the UEFI variable store on MMC as well, > since the UEFI runtime services routines expect ownership of the underlying > device as well. > > This series proposes an approach to work around this. It implements the UEFI > MMC host protocol in the kernel, in a way that makes it possible to expose it > to the firmware. At the same time, the firmware needs be set up for this, i.e., > it needs to expose its MMC host protocol pointer via a UEFI configuration table, > so that the kernel can override it if it decides to expose this functionality > to the firmware. > > Note that these patches are based on patches in the EFI tree that are queued > for v4.9, which replace the runtime wrappers spinlock with a semaphore. This > allows us to sleep in the firmware callbacks. Would it be possible to implement the UEFI varstore more generally on top of the Linux pstore interface and then have a pstore backend on top of MMC? That could give us very similar behavior, but also a bit more flexibility. It would be a bit confusing to have the 'dmesg' pstore target on top of UEFI varstore which in turn is on top of pstore on MMC, but I think that's ok as long as we prevent recursion. Arnd -- 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
