On 2023-01-24 at 12:30:50 +0100, Marco Pagani wrote:
> This patch changes the show() method of the "state" sysfs attribute to
> return an error if the bridge's enable_show() op returns an error code.
> In this way, the userspace can distinguish between when the bridge is
> actually "enabled" (i.e., allowing signals to pass) or "disabled"
> (i.e., gating signals), or when there is an error (e.g., the state of
> the bridge cannot be determined).
Maybe we remove the example for "error" here. This patch is just to
propagate the errors from low level drivers.
>
> Currently, enable_show() returns an integer representing the bridge's
> state (enabled or disabled) or an error code. However, this integer
> value is interpreted in state_show() as a bool, resulting in the method
> printing "enabled" (i.e., the bridge allows signals to pass), without
> propagating the error, even when enable_show() returns an error code.
>
> Another possibility could be to change the signature of enable_show()
> to return a bool for symmetry with the enable_set() "setter" method.
> However, this would prevent enable_show() from returning error codes
Returning error codes is good to me.
> and may break the HPS bridge driver (altera-hps2fpga.c +53).
>
> Thanks
>
> Signed-off-by: Marco Pagani <marpagan@xxxxxxxxxx>
> ---
> drivers/fpga/fpga-bridge.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/fpga/fpga-bridge.c b/drivers/fpga/fpga-bridge.c
> index 727704431f61..5cd40acab5bf 100644
> --- a/drivers/fpga/fpga-bridge.c
> +++ b/drivers/fpga/fpga-bridge.c
> @@ -293,12 +293,15 @@ static ssize_t state_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> struct fpga_bridge *bridge = to_fpga_bridge(dev);
> - int enable = 1;
> + int state = 1;
>
> - if (bridge->br_ops && bridge->br_ops->enable_show)
> - enable = bridge->br_ops->enable_show(bridge);
> + if (bridge->br_ops && bridge->br_ops->enable_show) {
> + state = bridge->br_ops->enable_show(bridge);
> + if (state < 0)
> + return state;
> + }
>
> - return sprintf(buf, "%s\n", enable ? "enabled" : "disabled");
> + return sysfs_emit(buf, "%s\n", state ? "enabled" : "disabled");
The code looks good to me. You may remove RFC prefix in next version.
Thanks,
Yilun
> }
>
> static DEVICE_ATTR_RO(name);
> --
> 2.39.1
>
