Re: [PATCH 03/10] driver core: Flow the return code from ->probe() through to sysfs bind

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Mon, Jun 07, 2021 at 09:55:45PM -0300, Jason Gunthorpe wrote:
> Currently really_probe() returns 1 on success and 0 if the probe() call
> fails. This return code arrangement is designed to be useful for
> __device_attach_driver() which is walking the device list and trying every
> driver. 0 means to keep trying.
> 
> However, it is not useful for the other places that call through to
> really_probe() that do actually want to see the probe() return code.
> 
> For instance bind_store() would be better to return the actual error code
> from the driver's probe method, not discarding it and returning -ENODEV.

Why does that matter?  Why does it need to know this?

> Reorganize things so that really_probe() always returns an error code on
> failure and 0 on success. Move the special code for device list walking
> into the walker callback __device_attach_driver() and trigger it based on
> an output flag from really_probe(). Update the rest of the API surface to
> return a normal -ERR or 0 on success.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>  drivers/base/bus.c |  6 +----
>  drivers/base/dd.c  | 61 ++++++++++++++++++++++++++++++----------------
>  2 files changed, 41 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/base/bus.c b/drivers/base/bus.c
> index 36d0c654ea6124..03591f82251302 100644
> --- a/drivers/base/bus.c
> +++ b/drivers/base/bus.c
> @@ -212,13 +212,9 @@ static ssize_t bind_store(struct device_driver *drv, const char *buf,
>  	dev = bus_find_device_by_name(bus, NULL, buf);
>  	if (dev && dev->driver == NULL && driver_match_device(drv, dev)) {
>  		err = device_driver_attach(drv, dev);
> -
> -		if (err > 0) {
> +		if (!err) {
>  			/* success */
>  			err = count;
> -		} else if (err == 0) {
> -			/* driver didn't accept device */
> -			err = -ENODEV;
>  		}
>  	}
>  	put_device(dev);
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index c1a92cff159873..7fb58e6219b255 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -513,7 +513,13 @@ static ssize_t state_synced_show(struct device *dev,
>  }
>  static DEVICE_ATTR_RO(state_synced);
>  
> -static int really_probe(struct device *dev, struct device_driver *drv)
> +enum {
> +	/* Set on output if the -ERR has come from a probe() function */
> +	PROBEF_DRV_FAILED = 1 << 0,
> +};
> +
> +static int really_probe(struct device *dev, struct device_driver *drv,
> +			unsigned int *flags)

Ugh, no, please no functions with random "flags" in them, that way lies
madness and unmaintainable code for decades to come.

Especially as I have no idea what this is trying to solve here at all...

greg k-h