linux-kernel - Re: can: ucan: Use usb_endpoint_type() rather than duplicating its implementation

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Message-ID: <1e64bcef-33f1-4295-b91f-d4598b32b866@web.de>
Date: Thu, 26 Jun 2025 09:22:17 +0200
From: Markus Elfring <Markus.Elfring@....de>
To: Vincent Mailhol <mailhol.vincent@...adoo.fr>, linux-can@...r.kernel.org
Cc: LKML <linux-kernel@...r.kernel.org>, kernel-janitors@...r.kernel.org,
 Chen Ni <nichen@...as.ac.cn>, Marc Kleine-Budde <mkl@...gutronix.de>
Subject: Re: can: ucan: Use usb_endpoint_type() rather than duplicating its
 implementation

>> I am unsure if the check reordering would be desirable for this function implementation.
> 
> Ah, you want to confirm whether
> 
>   usb_endpoint_dir_in(ep) && usb_endpoint_xfer_bulk(ep)
> 
> is the same as
> 
>   usb_endpoint_xfer_bulk(ep) && usb_endpoint_dir_in(ep)
> 
> ?

Exactly, yes.

Commutativity can probably be applied in this case.
But the different execution order will influence the corresponding run time characteristics.
https://en.wikipedia.org/wiki/Short-circuit_evaluation
https://en.wikipedia.org/wiki/Commutative_property

The data processing order from known API function implementations might get priority
also at discussed source code places in the near future.

Regards,
Markus