i2c: mux: pca954x: fix i2c mux selection caching
smbus functions return -ve on error, 0 on success. However, __i2c_transfer() have a different return signature - -ve on error, or number of buffers transferred (which may be zero or greater.) The upshot of this is that the sense of the test is reversed when using the mux on a bus supporting the master_xfer method: we cache the value and never retry if we fail to transfer any buffers, but if we succeed, we clear the cached value. Fix this by making pca954x_reg_write() return a negative error code for all failure cases. Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure") Acked-by: Peter Rosin <peda@axentia.se> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk> Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
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@ -167,6 +167,9 @@ static int pca954x_reg_write(struct i2c_adapter *adap,
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buf[0] = val;
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msg.buf = buf;
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ret = __i2c_transfer(adap, &msg, 1);
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if (ret >= 0 && ret != 1)
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ret = -EREMOTEIO;
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} else {
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union i2c_smbus_data data;
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ret = adap->algo->smbus_xfer(adap, client->addr,
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@ -195,7 +198,7 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan)
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/* Only select the channel if its different from the last channel */
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if (data->last_chan != regval) {
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ret = pca954x_reg_write(muxc->parent, client, regval);
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data->last_chan = ret ? 0 : regval;
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data->last_chan = ret < 0 ? 0 : regval;
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}
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return ret;
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