i2c: quirks: add zero length checks

Some adapters do not support a message length of 0. Add this as a quirk
so drivers don't have to open code it.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 02d6f27..a26b3e9 100644 (file)
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1839,9 +1839,15 @@ static int i2c_check_for_quirks(struct i2c_adapter *adap, struct i2c_msg *msgs,
                if (msgs[i].flags & I2C_M_RD) {
                        if (do_len_check && i2c_quirk_exceeded(len, q->max_read_len))
                                return i2c_quirk_error(adap, &msgs[i], "msg too long");
+
+                       if (q->flags & I2C_AQ_NO_ZERO_LEN_READ && len == 0)
+                               return i2c_quirk_error(adap, &msgs[i], "no zero length");
                } else {
                        if (do_len_check && i2c_quirk_exceeded(len, q->max_write_len))
                                return i2c_quirk_error(adap, &msgs[i], "msg too long");
+
+                       if (q->flags & I2C_AQ_NO_ZERO_LEN_WRITE && len == 0)
+                               return i2c_quirk_error(adap, &msgs[i], "no zero length");
                }
        }
 

diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index bc8d42f..2a98d08 100644 (file)
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -661,6 +661,10 @@ struct i2c_adapter_quirks {
                                         I2C_AQ_COMB_READ_SECOND | I2C_AQ_COMB_SAME_ADDR)
 /* clock stretching is not supported */
 #define I2C_AQ_NO_CLK_STRETCH          BIT(4)
+/* message cannot have length of 0 */
+#define I2C_AQ_NO_ZERO_LEN_READ                BIT(5)
+#define I2C_AQ_NO_ZERO_LEN_WRITE       BIT(6)
+#define I2C_AQ_NO_ZERO_LEN             (I2C_AQ_NO_ZERO_LEN_READ | I2C_AQ_NO_ZERO_LEN_WRITE)
 
 /*
  * i2c_adapter is the structure used to identify a physical i2c bus along