Re: [RFC PATCH 7/7] i2c: core: hand over reserved devices when requesting ancillary addresses

Geert Uytterhoeven
2020-02-21T10:14:02Z

Hi Wolfram,

On Thu, Feb 20, 2020 at 6:26 PM Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
> With i2c_new_ancillary_address, we can check if the intended driver is
> requesting a reserved address. Update the function to do these checks.
> If the check passes, the "reserved" device will become a regular "dummy"
> device.
>
> Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Thanks for your patch!

> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -975,6 +975,8 @@ struct i2c_client *i2c_new_ancillary_device(struct i2c_client *client,
> u16 default_addr)
> {
> struct device_node *np = client->dev.of_node;
> + struct device *reserved_dev, *adapter_dev = &client->adapter->dev;
> + struct i2c_client *reserved_client;
> u32 addr = default_addr;
> int i;
>
> @@ -984,7 +986,21 @@ struct i2c_client *i2c_new_ancillary_device(struct i2c_client *client,
> of_property_read_u32_index(np, "reg", i, &addr);
> }
>
> - dev_dbg(&client->adapter->dev, "Address for %s : 0x%x\n", name, addr);
> + dev_info(adapter_dev, "Address for %s : 0x%x\n", name, addr);
> +
> + /* No need to scan muxes, siblings must sit on the same adapter */
> + reserved_dev = device_find_child(adapter_dev, &addr, __i2c_check_addr_busy);
> + reserved_client = i2c_verify_client(reserved_dev);
> +
> + if (reserved_client) {
> + if (reserved_client->dev.of_node != np ||
> + strcmp(reserved_client->name, I2C_RESERVED_DRV_NAME) != 0)
> + return ERR_PTR(-EBUSY);

Missing put_device(reserved_dev).

> +
> + strlcpy(reserved_client->name, I2C_DUMMY_DRV_NAME, sizeof(client->name));
> + return reserved_client;
> + }

else put_device(reserved_dev)

(perhaps i2c_verify_client() checking dev was not such a great idea, as
callers need to act on dev && !verified anyway?)

> +
> return i2c_new_dummy_device(client->adapter, addr);
> }
> EXPORT_SYMBOL_GPL(i2c_new_ancillary_device);

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds