linux-kernel - Re: [PATCH] RDMA/siw: fix pointer cast warning

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Date:   Fri, 16 Dec 2022 08:46:16 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Bernard Metzler <bmt@...ich.ibm.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RDMA/siw: fix pointer cast warning

On Thu, Dec 15, 2022 at 6:03 PM Arnd Bergmann <arnd@...nel.org> wrote:

> From: Arnd Bergmann <arnd@...db.de>
>
> The previous build fix left a remaining issue in configurations
> with 64-bit dma_addr_t on 32-bit architectures:
>
> drivers/infiniband/sw/siw/siw_qp_tx.c: In function 'siw_get_pblpage':
> drivers/infiniband/sw/siw/siw_qp_tx.c:32:37: error: cast to pointer from integer of different size [-Werror=int-to-pointer-cast]
>    32 |                 return virt_to_page((void *)paddr);
>       |                                     ^
>
> Use the same double cast here that the driver uses elsewhere
> to convert between dma_addr_t and void*.
>
> It took me a while to figure out why this driver does it
> like this, as there is no hardware access and it just stores
> kernel pointers in place of device addresses when communicating
> with the rdma core and with user space.
>
> Fixes: 0d1b756acf60 ("RDMA/siw: Pass a pointer to virt_to_page()")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

This driver is a big confusion for me too.

Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij