linux-kernel - Re: [PATCH v2] nvmem: u-boot-env: improve error checking

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Date: Tue, 30 Jan 2024 16:25:36 -0700
From: Nick Spooner <nicholas.spooner@...gate.com>
To: rafal@...ecki.pl
Cc: dan.carpenter@...aro.org,
	evan.burgess@...gate.com,
	kernel-janitors@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	nicholas.spooner@...gate.com,
	srinivas.kandagatla@...aro.org
Subject: Re: [PATCH v2] nvmem: u-boot-env: improve error checking

Hi Rafał,

> I'd appreciate description why do we need this change other than
> addressing some Coverity report.

I've been looking at Coverity for bugs to fix when it was brought up on
the kernel-janitors mailing list as a way to gain experience with the
kernel tree. This issue stood out to me specifically because all other
instances of nvmem_add_one_cell (in core.c, onie-tlv.c, and sl28vpd.c) are
checked for errors. I figured I'd add a check for the one in u-boot-env.c
so that they're all covered, but I understand if this is a case where we
don't want to try to fix something that isn't necessarily broken.

> Should a single nvmem_add_one_cell() failure result in not registering
> NVMEM device at all? Why?

I see that the only place where the return value of u_boot_env_add_cells
gets checked is in the same file on line 192, where u_boot_env_parse sets
err. The only time err won't be 0 is if info.name causes u_boot_env_add_cells
to return -ENOMEM. So is that the only case where err should be set, or
should err report if any cells failed to register? I followed the logic
backwards and found that .probe is set to whatever u_boot_env_probe return,
so I'm guessing it's a matter of what .probe should include or not. Let me
know if my logic is incorrect anywhere.

Thanks,
Nick Spooner