From: Michael Walle <michael@walle.cc>
To: andriy.shevchenko@linux.intel.com
Cc: djrscally@gmail.com, gregkh@linuxfoundation.org,
heikki.krogerus@linux.intel.com, lenb@kernel.org,
linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
nuno.sa@analog.com, rafael@kernel.org,
sakari.ailus@linux.intel.com,
Russell King <linux@armlinux.org.uk>,
Horatiu Vultur <horatiu.vultur@microchip.com>,
Michael Walle <michael@walle.cc>
Subject: Re: [PATCH v4 1/1] device property: Allow error pointer to be passed to fwnode APIs
Date: Mon, 14 Mar 2022 20:51:37 +0100 [thread overview]
Message-ID: <20220314195138.20036-1-michael@walle.cc> (raw)
In-Reply-To: <20220308123712.18613-1-andriy.shevchenko@linux.intel.com>
Hi Andy,
> Some of the fwnode APIs might return an error pointer instead of NULL
> or valid fwnode handle. The result of such API call may be considered
> optional and hence the test for it is usually done in a form of
>
> fwnode = fwnode_find_reference(...);
> if (IS_ERR(fwnode))
> ...error handling...
>
> Nevertheless the resulting fwnode may have bumped the reference count
> and hence caller of the above API is obliged to call fwnode_handle_put().
> Since fwnode may be not valid either as NULL or error pointer the check
> has to be performed there. This approach uglifies the code and adds
> a point of making a mistake, i.e. forgetting about error point case.
>
> To prevent this, allow an error pointer to be passed to the fwnode APIs.
>
> Fixes: 83b34afb6b79 ("device property: Introduce fwnode_find_reference()")
> Reported-by: Nuno Sá <nuno.sa@analog.com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Tested-by: Nuno Sá <nuno.sa@analog.com>
> Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> Acked-by: Nuno Sá <nuno.sa@analog.com>
This breaks SFP/phylink (using the lan966x switch) on my board. See below
for more details.
[..]
> @@ -480,15 +485,16 @@ int fwnode_property_get_reference_args(const struct fwnode_handle *fwnode,
> {
> int ret;
>
> + if (IS_ERR_OR_NULL(fwnode))
> + return -ENOENT;
> +
> ret = fwnode_call_int_op(fwnode, get_reference_args, prop, nargs_prop,
> nargs, index, args);
> + if (ret == 0)
Should this be "if (ret == 0 || IS_ERR_OR_NULL(fwnode->secondary))" ?
> + return ret;
>
> - if (ret < 0 && !IS_ERR_OR_NULL(fwnode) &&
> - !IS_ERR_OR_NULL(fwnode->secondary))
> - ret = fwnode_call_int_op(fwnode->secondary, get_reference_args,
> - prop, nargs_prop, nargs, index, args);
> -
> - return ret;
> + return fwnode_call_int_op(fwnode->secondary, get_reference_args, prop, nargs_prop,
> + nargs, index, args);
> }
> EXPORT_SYMBOL_GPL(fwnode_property_get_reference_args);
What happens before this patch is that sfp_bus_find_fwnode() will call
fwnode_property_get_reference_args() and the first calls return -ENOENT
which sfp_bus_find_fwnode() will handle in a special way. After your
patch, -EINVAL is returned, because fwnode_call_int_op() on
fwnode->secondary is always called regardless of the return value of
the original fwnode.
-michael
next prev parent reply other threads:[~2022-03-14 19:58 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-08 12:37 [PATCH v4 1/1] device property: Allow error pointer to be passed to fwnode APIs Andy Shevchenko
2022-03-08 14:36 ` Heikki Krogerus
2022-03-08 19:03 ` Rafael J. Wysocki
2022-03-14 19:51 ` Michael Walle [this message]
2022-03-15 11:16 ` Rafael J. Wysocki
2022-03-15 13:27 ` Andy Shevchenko
2022-04-06 13:35 ` Andy Shevchenko
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