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From: Arnd Bergmann <arnd@arndb.de>
To: Scott Branden <scott.branden@broadcom.com>
Cc: Luis Chamberlain <mcgrof@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	David Brown <david.brown@linaro.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Shuah Khan <shuah@kernel.org>,
	Bjorn Andersson <bjorn.andersson@linaro.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	linux-arm-msm@vger.kernel.org,
	Linux FS-devel Mailing List <linux-fsdevel@vger.kernel.org>,
	BCM Kernel Feedback <bcm-kernel-feedback-list@broadcom.com>,
	Olof Johansson <olof@lixom.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Dan Carpenter <dan.carpenter@oracle.com>,
	Colin Ian King <colin.king@canonical.com>,
	Kees Cook <keescook@chromium.org>, Takashi Iwai <tiwai@suse.de>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>
Subject: Re: [PATCH 5/7] bcm-vk: add bcm_vk UAPI
Date: Tue, 27 Aug 2019 15:54:36 +0200
Message-ID: <CAK8P3a0QaYFCFkFSx5yOq-E-pt3tXdgMVKQM+POQK5ADN=b8qg@mail.gmail.com> (raw)
In-Reply-To: <20190822192451.5983-6-scott.branden@broadcom.com>

On Thu, Aug 22, 2019 at 9:25 PM Scott Branden
<scott.branden@broadcom.com> wrote:
>
> Add user space api for bcm-vk driver.

> +
> +struct vk_metadata {
> +       /* struct version, always backwards compatible */
> +       __u32 version;
> +
> +       /* Version 0 fields */
> +       __u32 card_status;
> +#define VK_CARD_STATUS_FASTBOOT_READY BIT(0)
> +#define VK_CARD_STATUS_FWLOADER_READY BIT(1)
> +
> +       __u32 firmware_version;
> +       __u32 fw_status;
> +       /* End version 0 fields */
> +
> +       __u64 reserved[14];
> +       /* Total of 16*u64 for all versions */
> +};

I'd suggest getting rid of the API version fields, just leave the version 0
fields here and add a new structure + ioctl if you need other
fields

Versioning usually just adds complexity and is hard to get right.

> +struct vk_access {
> +       __u8 barno;     /* BAR number to use */
> +       __u8 type;      /* Type of access */
> +#define VK_ACCESS_READ 0
> +#define VK_ACCESS_WRITE 1
> +       __u32 len;      /* length of data */
> +       __u64 offset;   /* offset in BAR */
> +       __u32 *data;    /* where to read/write data to */
> +};

The pointer in the last member makes the structure incompatible between
32-bit and 64-bit user space. You could work around that using a __u64
member and turning that into a pointer using the u64_to_user_ptr()
macro in the driver in a portable way.

However, since this seems to be a read/write type interface, maybe
it's better to just use read/write file operations.

I also wonder if the interface should be on a higher abstraction level
here.

      Arnd

  reply index

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-22 19:24 [PATCH 0/7] firmware: add partial read support in request_firmware_into_buf Scott Branden
2019-08-22 19:24 ` [PATCH 1/7] fs: introduce kernel_pread_file* support Scott Branden
2019-08-23 12:29   ` Takashi Iwai
2019-08-23 19:55     ` Scott Branden
2019-08-23 21:29       ` Luis Chamberlain
2019-08-22 19:24 ` [PATCH 2/7] firmware: add offset to request_firmware_into_buf Scott Branden
2019-08-22 19:47   ` Luis Chamberlain
2019-08-22 20:07     ` Scott Branden
2019-08-22 21:12       ` Luis Chamberlain
2019-08-22 23:30         ` Scott Branden
2019-08-23 15:47           ` Luis Chamberlain
2019-08-23 20:16             ` Scott Branden
2019-08-23 10:05   ` Takashi Iwai
2019-08-23 19:44     ` Scott Branden
2019-08-26 15:20       ` Takashi Iwai
2019-08-26 15:41         ` Scott Branden
2019-08-26 15:57           ` Takashi Iwai
2019-08-26 17:12           ` Takashi Iwai
2019-08-26 17:24             ` Scott Branden
2019-08-27 10:40               ` Takashi Iwai
2019-10-11 13:31                 ` Luis Chamberlain
2019-08-22 19:24 ` [PATCH 3/7] test_firmware: add partial read support for request_firmware_into_buf Scott Branden
2019-08-22 19:24 ` [PATCH 4/7] selftests: firmware: Test partial file reads of request_firmware_into_buf Scott Branden
2019-08-22 19:24 ` [PATCH 5/7] bcm-vk: add bcm_vk UAPI Scott Branden
2019-08-27 13:54   ` Arnd Bergmann [this message]
2019-08-27 14:49   ` Kieran Bingham
2019-10-08 15:59     ` Olof Johansson
2019-08-22 19:24 ` [PATCH 6/7] misc: bcm-vk: add Broadcom Valkyrie driver Scott Branden
2019-08-27 14:14   ` Arnd Bergmann
2019-08-27 15:25     ` Nicolas Dufresne
2019-08-22 19:24 ` [PATCH 7/7] MAINTAINERS: bcm-vk: Add maintainer for Broadcom Valkyrie Driver Scott Branden

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