[PATCH] i2c: mux: pca954x: fix i2c mux selection caching
From: Peter Rosin <hidden>
Date: 2016-12-16 21:20:35
Also in:
linux-i2c
On 2016-12-16 21:06, Russell King wrote:
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.
Ouch! Thanks for catching this.
Fix this.
But lets fix the corner case of __i2c_transfer returning 0 instead of the expected 1 as well (not sure if that's even possible, but lets close the possibility just in case), so I'd prefer if you could fix pca954x_reg_write() to return 0 iff __i2c_transfer(...) returns 1 instead, and -EREMOTEIO on other non-negative return values. Thanks! Cheers, peda
quoted hunk ↗ jump to hunk
Fixes: 463e8f845cbf ("i2c: mux: pca954x: retry updating the mux selection on failure") Signed-off-by: Russell King <redacted> --- drivers/i2c/muxes/i2c-mux-pca954x.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 8bc3d36d2837..b6d62ecbd5b6 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c@@ -179,7 +179,7 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan) /* Only select the channel if its different from the last channel */ if (data->last_chan != regval) { ret = pca954x_reg_write(muxc->parent, client, regval); - data->last_chan = ret ? 0 : regval; + data->last_chan = ret >= 0 ? regval : 0; } return ret;