Hi Alexey, On 29 May 2018 at 13:16, Alexey Brodkin <alexey.brod...@synopsys.com> wrote: > Hi Simon, > > On Fri, 2018-05-25 at 20:07 -0600, Simon Glass wrote: >> Hi Alexey, >> >> On 25 May 2018 at 03:45, Alexey Brodkin <alexey.brod...@synopsys.com> wrote: >> > Hi Simon, >> > >> > On Thu, 2018-05-24 at 20:42 -0600, Simon Glass wrote: >> > > Hi Alexey, > > [snip] > >> > > When we want to use a particular I2C bus via regmap, we could bind the >> > > I2C -> regmap driver as a child of the I2C bus driver. >> > >> > I guess that will require us to do corresponding changes in Device Tree >> > descriptions, right? And that will deviate those .dts-es from their kernel >> > counterparts [if they exist for a particular board]. >> >> Actually I don't think so. You can have a helper function that you >> call to bind the regmap to an I2C device, for example. That can be >> called from code, without needing any DT changes. > > So this helper function will be regmap_init_i2c(), right? > >> My objection is mostly to using function pointers to call what look >> like driver functions. The design of DM in U-Boot is supposed to >> support child drivers for exactly this purpose. So we should try to >> use it, unless we hit some terrible design flaw. > > Ok that makes sense. As you proposed we'll have new UCLASS like > UCLASS_SIMPLE_REG and within that class we'll have drivers that access > registers via memory, i2c, spi etc... that's quite clear. > > But what is not very obvious for me is that part about binding with > "master" devices. Could you please sketch something so I may get a better > picture?
Yes that sounds right. Basically this interface defines the operations in your UCLASS_SIMPLE_REG uclass: + int (*reg_read)(struct regmap *map, uint reg, uint *val); + int (*reg_write)(struct regmap *map, uint reg, uint val); Then you have different drivers that implement that uclass as you say (i2c, spi). The I2C simple_reg driver will require an I2C device to work with. This can be its parent device. To bind the device you'll need to call a function like: int simple_reg_i2c_bind(struct udevice *i2c_dev, struct udevice **devp) which calls device_bind(), or similar, to bind a new device as a child of i2c_dev, with uclass UCLASS_SIMPLE_REG. Then the device can be probed, The I2C simple_reg driver can implement the reg_read() method by calling dm_i2c_read() on its parent. You can put simple_reg_i2c_bind() in the regmap code perhaps, or maybe there is a better place for it. You should make sure there is a sandbox test which creates a device and checks that it can read and write a few registers. Does that explain it? Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
