linux-kernel - Re: [PATCH v5] hid-mcp2200: added driver for GPIOs of MCP2200

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20230831185343.211651-1-johannes@gnu-linux.rocks>
Date:   Thu, 31 Aug 2023 20:53:43 +0200
From:   Johannes Roith <johannes@...-linux.rocks>
To:     sergeantsagara@...tonmail.com
Cc:     ak@...klinger.de, andi.shyti@...nel.org,
        benjamin.tissoires@...hat.com, christophe.jaillet@...adoo.fr,
        jikos@...nel.org, johannes@...-linux.rocks,
        linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        rdunlap@...radead.org
Subject: Re: [PATCH v5] hid-mcp2200: added driver for GPIOs of MCP2200

Hi Rahul,

thanks for the feedback, I will add it to the driver.

> My personal recommendation is to just have a single DMA buffer allocated
> for the mcp2200 instance rather than having to call the allocator and
> release the memory per command.

I added an 16-byte Array hid_report to the mcp2000 struct. When I need the
report, I do the following:

struct mcp_set_clear_outputs *cmd;

mutex_lock(&mcp->lock);
cmd = (struct mcp_set_clear_outputs *) mcp->hid_report

Do you think this is a valid implementation or do I really have to add a
pointer to the mcp2200 struct instead of the 16 byte array and allocate 
another 16 byte for it in the probe function?

> The reason you run into this is likely because of the action added to
> devm conflicting with hid_device_remove....
> 
> I recommend not depending on devm for teardown rather than making a stub
> remove function to work around the issue.

I am not sure, if I have understand this correctly, but basically I already
have a stub remove function (which is empty). First the remove function gets
called, then the unregister function and everything is cleaned up correctly.
Did I get this right or do you have any other recommendation for me?

So, do I need any adaptions, or can we go with the empty remove function?

Best regards,
Johannes