Re: [dpdk-dev] [PATCH v4] ethdev: add sanity checks in control APIs

From: Thomas Monjalon <thomas@monjalon.net>
To: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
Cc: "Min Hu (Connor)" <humin29@huawei.com>,
	dev@dpdk.org, ferruh.yigit@intel.com
Subject: Re: [dpdk-dev] [PATCH v4] ethdev: add sanity checks in control APIs
Date: Thu, 15 Apr 2021 13:57:42 +0200	[thread overview]
Message-ID: <2252218.jVnlyW2HoW@thomas> (raw)
In-Reply-To: <b9b84f59-686f-bc1b-89a0-c914bcfae4a1@oktetlabs.ru>

15/04/2021 10:15, Andrew Rybchenko:
> >  	RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->dev_configure, -ENOTSUP);
> 
> In theory, the first argument is sufficient to make the ops
> check, but I think it is the right solution to keep it as is
> since current tendency is to check operation support when
> driver callback is really required and we're going to use it.
> However, if we do it just after port_id check, we'll have a
> way to check for callback support without any side effects
> if we provide invalid argument value. I.e. if -ENOTSUP is
> returned, callback is not supported, if -EINVAL, callback is
> supported (but argument is invalid and nothing done).
> However, it looks a bit fragile and not always possible.
> Thoughts on it are welcome.

Sorry I don't understand it fully.
You say we should check for ENOTSUP at the very beginning?