From mboxrd@z Thu Jan 1 00:00:00 1970 From: boris.brezillon@bootlin.com (Boris Brezillon) Date: Tue, 21 Aug 2018 15:57:31 +0200 Subject: [PATCH v2 06/29] mtd: Add support for reading MTD devices via the nvmem API In-Reply-To: References: <20180810080526.27207-1-brgl@bgdev.pl> <20180810080526.27207-7-brgl@bgdev.pl> <20180817182720.6a6e5e8e@bbrezillon> <20180819133106.0420df5f@tock> <20180819184609.6dcdbb9a@bbrezillon> <20180821005327.0d312a85@tock> <20180821074404.23aaeb6b@bbrezillon> <81407b4d-a02f-4085-f333-a96102bd96ce@linaro.org> <20180821133136.1fada1b6@bbrezillon> <6fb36da4-c985-6d6e-f9e1-572f5cd7609b@linaro.org> Message-ID: <20180821155731.11cae21b@bbrezillon> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 21 Aug 2018 14:37:37 +0100 Srinivas Kandagatla wrote: > On 21/08/18 14:34, Srinivas Kandagatla wrote: > > > > > > On 21/08/18 12:31, Boris Brezillon wrote: > >>> * struct nvmem_config - NVMEM device configuration > >>> @@ -58,6 +62,7 @@ struct nvmem_config { > >>> bool root_only; > >>> nvmem_reg_read_t reg_read; > >>> nvmem_reg_write_t reg_write; > >>> + nvmem_match_t match; > >>> int size; > >>> int word_size; > >>> int stride; > >>> > >> That might work if nvmem cells are defined directly under the mtdnode. > > Layout should not matter! which is the purpose of this callback. > > > > The only purpose of this callback is to tell nvmem core that the > > node(nvmem cell) belongs to that provider or not, if it is then we > > successfully found the provider. Its up to the provider on which layout > > it describes nvmem cells. Additionally the provider can add additional > > sanity checks in this match function to ensure that cell is correctly > > represented. > > > > > >> If we go for this approach, I'd recommend replacing this ->match() hook > >> by ->is_nvmem_cell() and pass it the cell node instead of the nvmem > >> node, because what we're really after here is knowing which subnode is > >> an nvmem cell and which subnode is not. > > > > I agree on passing cell node instead of its parent. Regarding basic > > validating if its nvmem cell or not, we can check compatible string in > > nvmem core if we decide to use "nvmem-cell" compatible. > > > > Also just in case if you missed this, nvmem would not iterate the > Sorry !! i hit send button too quickly I guess. > > What I meant to say here, is that nvmem core would not iterate the > provider node in any case. > > Only time it looks at the cell node is when a consumer requests for the > cell. I did miss that, indeed. Thanks for the heads up. So, the "old partitions being considered as nvmem cells" is not really a problem, because those parts shouldn't be referenced. This leaves us with the config->force_compat_check topic, which I'd like to have to ensure that nvmem cells under MTD nodes actually have compatible = "nvmem-cell" and prevent people from inadvertently omitting this prop. And of course, we need Rob's approval on this new binding :-).