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SubjectRe: [PATCH v1 2/5] driver core: Set deferred probe reason when deferred by driver core
Hi Saravana,

On Tue, Sep 14, 2021 at 6:39 AM Saravana Kannan <saravanak@google.com> wrote:
> When the driver core defers the probe of a device, set the deferred
> probe reason so that it's easier to debug. The deferred probe reason is
> available in debugfs under devices_deferred.
>
> Signed-off-by: Saravana Kannan <saravanak@google.com>

Thanks for your patch!

> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -955,6 +955,29 @@ static void device_links_missing_supplier(struct device *dev)
> }
> }
>
> +/**
> + * dev_set_def_probe_reason - Set the deferred probe reason for a device
> + * @dev: the pointer to the struct device
> + * @fmt: printf-style format string
> + * @...: arguments as specified in the format string
> + *
> + * This is a more caller-friendly version of device_set_deferred_probe_reason()
> + * that takes variable argument inputs similar to dev_info().
> + */
> +static void dev_set_def_probe_reason(const struct device *dev, const char *fmt, ...)

So this is indeed similar to device_set_deferred_probe_reason(),
but the function's name is completely different, unlike e.g.
(v)printf()?

> +{
> + struct va_format vaf;
> + va_list args;
> +
> + va_start(args, fmt);
> + vaf.fmt = fmt;
> + vaf.va = &args;
> +
> + device_set_deferred_probe_reason(dev, &vaf);
> +
> + va_end(args);
> +}

I think you can just make this a macro wrapper calling
dev_err_probe(dev, -EPROBE_DEFER, fmt, ...).
Or open-code that below.

> +
> /**
> * device_links_check_suppliers - Check presence of supplier drivers.
> * @dev: Consumer device.
> @@ -975,6 +998,7 @@ int device_links_check_suppliers(struct device *dev)
> {
> struct device_link *link;
> int ret = 0;
> + struct fwnode_handle *sup_fw;
>
> /*
> * Device waiting for supplier to become available is not allowed to
> @@ -983,10 +1007,13 @@ int device_links_check_suppliers(struct device *dev)
> mutex_lock(&fwnode_link_lock);
> if (dev->fwnode && !list_empty(&dev->fwnode->suppliers) &&
> !fw_devlink_is_permissive()) {
> + sup_fw = list_first_entry(&dev->fwnode->suppliers,
> + struct fwnode_link,
> + c_hook)->supplier;
> dev_dbg(dev, "probe deferral - wait for supplier %pfwP\n",
> - list_first_entry(&dev->fwnode->suppliers,
> - struct fwnode_link,
> - c_hook)->supplier);
> + sup_fw);
> + dev_set_def_probe_reason(dev,
> + "wait for supplier %pfwP\n", sup_fw);

dev_err_probe() would replace both the dev_dbg() and the
dev_set_def_probe_reason().

> mutex_unlock(&fwnode_link_lock);
> return -EPROBE_DEFER;
> }
> @@ -1003,6 +1030,9 @@ int device_links_check_suppliers(struct device *dev)
> device_links_missing_supplier(dev);
> dev_dbg(dev, "probe deferral - supplier %s not ready\n",
> dev_name(link->supplier));
> + dev_set_def_probe_reason(dev,
> + "supplier %s not ready\n",
> + dev_name(link->supplier));

Likewise.

> ret = -EPROBE_DEFER;
> break;
> }

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds

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