linux-kernel - Re: Should dma_map_single take the dma controller or its consumer as an argument?

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

Message-ID: <ZJwTV59xRlUBit+N@shell.armlinux.org.uk>
Date:   Wed, 28 Jun 2023 12:02:47 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Li Chen <me@...ux.beauty>
Cc:     dmaengine <dmaengine@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: Should dma_map_single take the dma controller or its consumer as
 an argument?

On Wed, Jun 28, 2023 at 06:57:35PM +0800, Li Chen wrote:
> Hi all,
> 
> I recently encountered an issue where the dma_mask was set in the DMA controller's driver, but the consumer peripheral driver didn't set its own dma_mask.

It should always take the device that is *actually* performing the DMA,
since that is the device that has restrictions on what addresses can be
accessed, etc.

Devices that "consume" the data from a DMA controller don't access
memory - they are merely the targets, and they can't on their own access
host memory. Therefore, their dma mask _should_ be irrelevant.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!