linux-kernel - Re: [PATCH 4/7] ARM: remove the unused virt_to

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Message-ID: <CAK8P3a2zSZsiq_FFHJMHex6uLc_7sUfvns8W8-mE52yzxOqhKw@mail.gmail.com>
Date:   Thu, 21 Apr 2022 10:00:55 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Russell King <linux@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andre Przywara <andre.przywara@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        "open list:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        USB list <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 4/7] ARM: remove the unused virt_to_dma helper

On Thu, Apr 21, 2022 at 9:42 AM Christoph Hellwig <hch@....de> wrote:
>
> Signed-off-by: Christoph Hellwig <hch@....de>

I generally prefer to have at least something useful in the description, e.g.
why it's now unused and what it was used for before.

> -static inline dma_addr_t virt_to_dma(struct device *dev, void *addr)
> -{
> -       if (dev)
> -               return pfn_to_dma(dev, virt_to_pfn(addr));
> -
> -       return (dma_addr_t)__virt_to_bus((unsigned long)(addr));
> -}

I think __virt_to_bus() is now unused as well and could be removed
in the same step.

It looks like __bus_to_virt() is still used in the ISA DMA API, but
as that is only used on footbridge and rpc, the generic version of
that could be moved into rpc (footbridge already has a custom
version).

    Arnd