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Miller" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2018-08-25 8:27 GMT+02:00 Boris Brezillon : > On Fri, 24 Aug 2018 17:27:40 +0200 > Andrew Lunn wrote: > >> On Fri, Aug 24, 2018 at 05:08:48PM +0200, Boris Brezillon wrote: >> > Hi Bartosz, >> > >> > On Fri, 10 Aug 2018 10:04:58 +0200 >> > Bartosz Golaszewski wrote: >> > >> > > +struct nvmem_cell_lookup { >> > > + struct nvmem_cell_info info; >> > > + struct list_head list; >> > > + const char *nvmem_name; >> > > +}; >> > >> > Hm, maybe I don't get it right, but this looks suspicious. Usually the >> > consumer lookup table is here to attach device specific names to >> > external resources. >> > >> > So what I'd expect here is: >> > >> > struct nvmem_cell_lookup { >> > /* The nvmem device name. */ >> > const char *nvmem_name; >> > >> > /* The nvmem cell name */ >> > const char *nvmem_cell_name; >> > >> > /* >> > * The local resource name. Basically what you have in the >> > * nvmem-cell-names prop. >> > */ >> > const char *conid; >> > }; >> > >> > struct nvmem_cell_lookup_table { >> > struct list_head list; >> > >> > /* ID of the consumer device. */ >> > const char *devid; >> > >> > /* Array of cell lookup entries. */ >> > unsigned int ncells; >> > const struct nvmem_cell_lookup *cells; >> > }; >> > >> > Looks like your nvmem_cell_lookup is more something used to attach cells >> > to an nvmem device, which is NVMEM provider's responsibility not the >> > consumer one. >> >> Hi Boris >> >> There are cases where there is not a clear providier/consumer split. I >> have an x86 platform, with a few at24 EEPROMs on it. It uses an off >> the shelf Komtron module, placed on a custom carrier board. One of the >> EEPROMs contains the hardware variant information. Once i know the >> variant, i need to instantiate other I2C, SPI, MDIO devices, all using >> platform devices, since this is x86, no DT available. >> >> So the first thing my x86 platform device does is instantiate the >> first i2c device for the AT24. Once the EEPROM pops into existence, i >> need to add nvmem cells onto it. So at that point, the x86 platform >> driver is playing the provider role. Once the cells are added, i can >> then use nvmem consumer interfaces to get the contents of the cell, >> run a checksum, and instantiate the other devices. >> >> I wish the embedded world was all DT, but the reality is that it is >> not :-( > > Actually, I'm not questioning the need for this feature (being able to > attach NVMEM cells to an NVMEM device on a platform that does not use > DT). What I'm saying is that this functionality is provider related, > not consumer related. Also, I wonder if defining such NVMEM cells > shouldn't go through the provider driver instead of being passed > directly to the NVMEM layer, because nvmem_config already have a fields > to pass cells at registration time, plus, the name of the NVMEM cell > device is sometimes created dynamically and can be hard to guess at > platform_device registration time. > In my use case the provider is at24 EEPROM driver. This is where the nvmem_config lives but I can't image a correct and clean way of passing this cell config to the driver from board files without using new ugly fields in platform_data which this very series is trying to remove. This is why this cell config should live in machine code. > I also think non-DT consumers will need a way to reference exiting > NVMEM cells, but this consumer-oriented nvmem cell lookup table should > look like the gpio or pwm lookup table (basically what I proposed in my > previous email). How about introducing two new interfaces to nvmem: one for defining nvmem cells from machine code and the second for connecting these cells with devices? Best regards, Bart