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Tue, 12 Oct 2021 13:31:25 -0700 (PDT) MIME-Version: 1.0 References: <20211001050228.55183-1-takahiro.akashi@linaro.org> <20211001050228.55183-24-takahiro.akashi@linaro.org> <20211011064336.GH44356@laputa> <6c6bec49-dbfd-c352-be21-4319d24db32c@gmx.de> <20211012020911.GD38222@laputa> In-Reply-To: <20211012020911.GD38222@laputa> From: Simon Glass Date: Tue, 12 Oct 2021 14:31:13 -0600 Message-ID: Subject: Re: [RFC 12/22] dm: add a hidden link to efi object To: AKASHI Takahiro , Simon Glass , 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 Takahiro, On Mon, 11 Oct 2021 at 20:09, AKASHI Takahiro wrote: > > On Mon, Oct 11, 2021 at 10:09:19AM -0600, Simon Glass wrote: > > Hi Heinrich, > > > > On Mon, 11 Oct 2021 at 09:31, Heinrich Schuchardt wrote: > > > > > > > > > > > > On 10/11/21 16:54, Simon Glass wrote: > > > > Hi Takahiro, > > > > > > > > On Mon, 11 Oct 2021 at 00:43, AKASHI Takahiro > > > > wrote: > > > >> > > > >> Simon, > > > >> > > > >> On Sun, Oct 10, 2021 at 08:14:18AM -0600, Simon Glass wrote: > > > >>> Hi Takahiro, > > > >>> > > > >>> On Thu, 30 Sept 2021 at 23:04, AKASHI Takahiro > > > >>> wrote: > > > >>>> > > > >>>> This member field in udevice will be used to dereference from udevice > > > >>>> to efi_object (or efi_handle). > > > >>>> > > > >>>> Signed-off-by: AKASHI Takahiro > > > >>>> --- > > > >>>> include/dm/device.h | 4 ++++ > > > >>>> 1 file changed, 4 insertions(+) > > > >>> > > > >>> I think this should be generalised. > > > >>> > > > >>> Can we add a simple API for attaching things to devices? Something like: > > > >> > > > >> Ok. > > > >> > > > >> > > > >>> config DM_TAG > > > >>> bool "Support tags attached to devices" > > > >>> > > > >>> enum dm_tag_t { > > > >>> DM_TAG_EFI = 0, > > > >>> > > > >>> DM_TAG_COUNT, > > > >>> }; > > > >>> > > > >>> ret = dev_tag_set_ptr(dev, DM_TAG_EFI, ptr); > > > >>> > > > >>> void *ptr = dev_tag_get_ptr(dev, DM_TAG_EFI); > > > >>> > > > >>> ulong val = dev_tag_get_val(dev, DM_TAG_EFI); > > > >>> > > > >>> Under the hood I think for now we could have a simple list of tags for > > > >>> all of DM: > > > >>> > > > >>> struct dmtag_node { > > > >>> struct list_head sibling; > > > >>> struct udevice *dev; > > > >>> enum dm_tag_t tag; > > > >>> union { > > > >>> void *ptr; > > > >>> ulong val; > > > >>> }; > > > >>> }; > > > >> > > > >> Just let me make sure; Do you intend that we have a *single* list of tags > > > >> in the system instead of maintaining a list *per udevice*? > > > > > > > > Yes I would prefer not to have a list per udevice, although the API > > > > could be adjusted to iterate through all tags for a particular > > > > udevice, if that is needed (dev_tag_first...() dev_tag_next...(). > > > > > > There will never be more than one UEFI handle for one udevice. > > > We need a single field that points to the the handle if such a handle > > > exists. But there will be devices for which UEFI protocols don't exist > > > and where we need no handle. In this case the value can be NULL. > > > > > > Why should we complicate the picture with a list of tags? > > > > Let's not talk about complexity while we are discussing UEFI :-) > > > > There are other cases where we need to add info to a device. We cover > > almost all the cases with the uclass-private, plat and priv data > > attached to each device. But in some cases that is not enough, > > While I'm not sure whether it is "not enough", I used to think of using > 'priv_auto' (or per_device_auto of UCLASS) to hold a pointer to efi_object, > but we might see a conflicting situation in the future where some driver > may also want to use 'priv_auto' for their own purpose. > That is why I added an extra member to udevice. Yes indeed, we are finding a few situations where there are not enough places to put data attached to devices. > > # The real benefit might be to keep the size of udevice unchanged? Yes, although I hope we can actually reduce it. Needs some analysis though. > > -Takahiro Akashi > > > as with > > EFI. I have hit this before in a few other places but have tried to > > work around it rather than extending driver model and adding to the > > already-large struct udevice. But I think we are at the end of the > > road on that. > > > > I'd also like to look at how much (for example) uclass-plat data is > > used for devices, in case it would be more efficient to move it to a > > tag model. > > > > I should also point out you are talking about the implementation > > rather than the API. We can always change the impl later, so long as > > we have a suitable API. > > > > > > > > > > Looking at some of your other patches I think you might need to > > > > support multiple tags for EFI, if there are different things. But > > > > perhaps a list is necesary. > > > > > > > >> > > > >> -Takahiro Akashi > > > >> > > > >> > > > >>> This can be useful in other situations, for example I think we need to > > > >>> be able to send an event when a device is probed so that other devices > > > >>> (with tags attached) can take action. But in any case, it makes the > > > >>> API separate from the data structure, so aids refactoring later. > > > >>> > > > >>> If we find that this is slow we can change the impl, but I doubt it > > > >>> will matter fornow. > > > >>> Regards, SImon