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Tue, 12 Oct 2021 16:37:56 -0700 (PDT) MIME-Version: 1.0 References: <20211001050228.55183-1-takahiro.akashi@linaro.org> <20211012150023.GY7964@bill-the-cat> <20211012211343.GH7964@bill-the-cat> In-Reply-To: <20211012211343.GH7964@bill-the-cat> From: Simon Glass Date: Tue, 12 Oct 2021 17:37:45 -0600 Message-ID: Subject: Re: [RFC 00/22] efi_loader: more tightly integrate UEFI disks to device model To: Tom Rini Cc: AKASHI Takahiro , Heinrich Schuchardt , Alex Graf , Ilias Apalodimas , U-Boot Mailing List Content-Type: text/plain; charset="UTF-8" X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.34 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.2 at phobos.denx.de X-Virus-Status: Clean Hi Tom, On Tue, 12 Oct 2021 at 15:13, Tom Rini wrote: > > On Tue, Oct 12, 2021 at 02:31:15PM -0600, Simon Glass wrote: > > Hi Tom, > > > > On Tue, 12 Oct 2021 at 09:00, Tom Rini wrote: > > > > > > On Sun, Oct 10, 2021 at 08:14:00AM -0600, Simon Glass wrote: > > > > Hi Takahiro, > > > > > > > > On Thu, 30 Sept 2021 at 23:02, AKASHI Takahiro > > > > wrote: > > > > > > > > > > The purpose of this RPC is to reignite the discussion about how UEFI > > > > > subystem would best be integrated into U-Boot device model. > > > > > In the past, I poposed a couple of patch series, the latest one[1], > > > > > while Heinrich revealed his idea[2], and the approach taken here is > > > > > something between them, with a focus on block device handlings. > > > > > > > > > > # The code is a PoC and not well tested yet. > > > > > > > > > > Disks in UEFI world: > > > > > ==================== > > > > > In general in UEFI world, accessing to any device is performed through > > > > > a 'protocol' interface which are installed to (or associated with) the device's > > > > > UEFI handle (or an opaque pointer to UEFI object data). Protocols are > > > > > implemented by either the UEFI system itself or UEFI drivers. > > > > > > > > > > For block IO's, it is a device which has EFI_BLOCK_IO_PROTOCOL (efi_disk > > > > > hereafter). Currently, every efi_disk may have one of two origins: > > > > > a.U-Boot's block devices or related partitions > > > > > (lib/efi_loader/efi_disk.c) > > > > > b.UEFI objects which are implemented as a block device by UEFI drivers. > > > > > (lib/efi_driver/efi_block_device.c) > > > > > > > > > > All the efi_diskss as (a) will be enumelated and created only once at UEFI > > > > > subsystem initialization (efi_disk_register()), which is triggered by > > > > > first executing one of UEFI-related U-Boot commands, like "bootefi", > > > > > "setenv -e" or "efidebug". > > > > > EFI_BLOCK_IO_PROTOCOL is implemented by UEFI system using blk_desc(->ops) > > > > > in the corresponding udevice(UCLASS_BLK). > > > > > > > > > > On the other hand, efi_disk as (b) will be created each time UEFI boot > > > > > services' connect_controller() is executed in UEFI app which, as a (device) > > > > > controller, gives the method to access the device's data, > > > > > ie. EFI_BLOCK_IO_PROTOCOL. > > > > > > > > > > >>> more details >>> > > > > > Internally, connect_controller() search for UEFI driver that can support > > > > > this controller/protocol, 'efi_block' driver(UCLASS_EFI) in this case, > > > > > then calls the driver's 'bind' interface, which eventually installs > > > > > the controller's EFI_BLOCK_IO_PROTOCOL to efi_disk object. > > > > > 'efi_block' driver also create a corresponding udevice(UCLASS_BLK) for > > > > > * creating additional partitions efi_disk's, and > > > > > * supporting a file system (EFI_SIMPLE_FILE_SYSTEM_PROTOCOL) on it. > > > > > <<< <<< > > > > > > > > > > Issues: > > > > > ======= > > > > > 1. While an efi_disk represents a device equally for either a whole disk > > > > > or a partition in UEFI world, the device model treats only a whole > > > > > disk as a real block device or udevice(UCLASS_BLK). > > > > > > > > > > 2. efi_disk holds and makes use of "blk_desc" data even though blk_desc > > > > > in plat_data is supposed to be private and not to be accessed outside > > > > > the device model. > > > > > # This issue, though, exists for all the implmenetation of U-Boot > > > > > # file systems as well. > > > > > > > > Yes, this was a migration convenience and we should be able to unpick it now. > > > > > > > > However we still have SPL_BLK so need to consider whether we can drop that. > > > > > > To be clear here, in that I can hand-wave my way to seeing a use case > > > for lib/efi_loader/ under SPL, it would not be in a world where we also > > > still would be supporting the non-DM infrastructure, and is also not a > > > near-term goal. > > > > OK good. Perhaps we should add a migration method for SPL_BLK? It > > would be good to know where we are in terms of the size stuff. I don't > > see a lot of boards rushing to use of-platdata, though. > > What do you mean? Since we have platforms that need to support 12 or 16 > KiB of space for SPL, we're not going to enforce SPL_DM. But those > platforms can / do need to boot from MMC (SD card I think usually). > > In terms of platforms that could, but don't, enable SPL_BLK, that's just > the platforms that disable SPL_BLK today as it defaults to enabled when > possible. Well I wonder if we can use of-platdata and DM then perhaps some of these will fit. The OMAP platform I sent patches for was close to complete, I think, and I believe that was one of the tightest. Actually I cannot remember what board that was... The overhead is perhaps 7KB though, so maybe not suitable for 16KB. Regards, Simon