[U-Boot] [PATCH v3 08/10] dm: Add a simple EEPROM driver

[Simon Glass]

Hi Masahiro,

On 1 December 2014 at 04:48, Masahiro Yamada <yamada.m at jp.panasonic.com> wrote:
> Hi Simon,
>
>
>
>
>
> On Mon, 24 Nov 2014 11:57:22 -0700
> Simon Glass <sjg at chromium.org> wrote:
>
>> --- /dev/null
>> +++ b/drivers/misc/i2c_eeprom.c
>> @@ -0,0 +1,51 @@
>> +/*
>> + * Copyright (c) 2014 Google, Inc
>> + *
>> + * SPDX-License-Identifier:  GPL-2.0+
>> + */
>> +
>> +#include <common.h>
>> +#include <dm.h>
>> +#include <i2c.h>
>> +#include <i2c_eeprom.h>
>> +
>> +static int i2c_eeprom_read(struct udevice *dev, int offset, uint8_t *buf,
>> +                        int size)
>> +{
>> +     return -ENODEV;
>> +}
>> +
>> +static int i2c_eeprom_write(struct udevice *dev, int offset,
>> +                         const uint8_t *buf, int size)
>> +{
>> +     return -ENODEV;
>> +}
>
>
> Isn't there any possibility to reach i2c_eeprom_read/i2c_eeprom_write
> handler?

No it's just a stub for now.

>
> Maybe, is it better to fallback to i2c_read()/i2c_write() like this?
>
>
> static int i2c_eeprom_read(struct udevice *dev, int offset, uint8_t *buf,
>                            int size)
> {
>         return i2c_read(dev, offset, buf, size);
> }
>
> static int i2c_eeprom_write(struct udevice *dev, int offset, const uint8_t *buf,
>                            int size)
> {
>         return i2c_write(dev, offset, buf, size);
> }
>
>

Sure we can - I haven't implemented this yet, but if we could have a
generic EEPROM driver like this it would be nice.

>
> Moreover, can we read data from EEPROM
> without knowing if its parent is I2C bus or SPI bus ?
>
>
> My rough image is like this:
>
> int eeprom_read(struct udevice *dev, int offset, uint8_t buf, int size)
> {
>         struct udevice *bus = dev->parent;
>         struct generic_bus_operation *ops = bus->uclass->uc_drv->ops;
>
>         return ops->read(dev, bus, offset, buf, size);
> }
>
> I am not sure, but if this approach is possible,
> we do not need to have both of "i2c_eeprom uclass" and "spi_eeprom uclass".
>
> struct generic_bus_operation is the operaton some uclasses have.
>
> We can move i2c_read() and i2c_write()
> to struct generic_bus_operation of i2c uclass.
>
> Likewise, we can move spi_read() and spi_write()
> to struct generic_bus_operation of spi uclass.

Yes we should do join up I2C and SPI. In order to do it we need SPI
uclass to support reading and writing a particular offset (rather than
just the current generic xfer()).

Perhaps we should have a generic register access uclass. Drivers that
want to support it could add themselves to the I2C and REGISTER
uclass. But it would be better to handle this entirely in the I2C/SPI
uclasses if we can.

I added Przemyslaw as he needs something like this for the PMIC uclass.

Regards,
Simon