From patchwork Mon Aug 5 06:22:00 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christopher James Halse Rogers X-Patchwork-Id: 2838559 Return-Path: X-Original-To: patchwork-dri-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id B11379F485 for ; Mon, 5 Aug 2013 07:07:27 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id CF6D12017D for ; Mon, 5 Aug 2013 07:07:26 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by mail.kernel.org (Postfix) with ESMTP id C6A1D2017B for ; Mon, 5 Aug 2013 07:07:25 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id AAD30E6279 for ; Mon, 5 Aug 2013 00:07:25 -0700 (PDT) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org X-Greylist: delayed 486 seconds by postgrey-1.32 at gabe; Sun, 04 Aug 2013 23:30:19 PDT Received: from mail.cooperteam.net (li226-30.members.linode.com [173.255.216.30]) by gabe.freedesktop.org (Postfix) with ESMTP id 875EBE5CB1 for ; Sun, 4 Aug 2013 23:30:19 -0700 (PDT) Received: from Bebop.fritz.box (ppp105-211.static.internode.on.net [150.101.105.211]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: chris) by mail.cooperteam.net (Postfix) with ESMTPSA id 1D9B0104B29; Mon, 5 Aug 2013 06:22:09 +0000 (UTC) From: Christopher James Halse Rogers To: linux-kernel@vger.kernel.org Subject: [PATCH] dma-buf: Expose buffer size to userspace Date: Mon, 5 Aug 2013 16:22:00 +1000 Message-Id: <1375683720-4748-1-git-send-email-christopher.halse.rogers@canonical.com> X-Mailer: git-send-email 1.8.3.2 Cc: linux-arch@vger.kernel.org, Christopher James Halse Rogers , dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, robclark@gmail.com, linux-media@vger.kernel.org X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: dri-devel-bounces+patchwork-dri-devel=patchwork.kernel.org@lists.freedesktop.org Errors-To: dri-devel-bounces+patchwork-dri-devel=patchwork.kernel.org@lists.freedesktop.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Each dma-buf has an associated size and it's reasonable for userspace to want to know what it is. Since userspace already has an fd, expose the size using the size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0); idiom. Signed-off-by: Christopher James Halse Rogers --- I've run into a point in the radeon DRM userspace where I need the size of a dma-buf. I could add a radeon-specific mechanism to get that, but this seems like something that would be more generally useful. I'm not entirely sure about supporting both SEEK_END and SEEK_CUR; this is somewhat of an abuse of lseek, as seeking obviously doesn't make sense. It's the obivous idiom for getting the size of what's on the other end of a file descriptor, though. I didn't notice anywhere to document this; Documentation/dma-buf-api didn't seem like the right place. Is there somewhere I've overlooked? drivers/base/dma-buf.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c index 6687ba7..c33a857 100644 --- a/drivers/base/dma-buf.c +++ b/drivers/base/dma-buf.c @@ -77,9 +77,36 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) return dmabuf->ops->mmap(dmabuf, vma); } +static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) +{ + struct dma_buf *dmabuf; + loff_t base; + + if (!is_dma_buf_file(file)) + return -EBADF; + + dmabuf = file->private_data; + + /* only support discovering the end of the buffer, + but also allow SEEK_SET to maintain the idiomatic + SEEK_END(0), SEEK_CUR(0) pattern */ + if (whence == SEEK_END) + base = dmabuf->size; + else if (whence == SEEK_SET) + base = 0; + else + return -EINVAL; + + if (offset != 0) + return -EINVAL; + + return base + offset; +} + static const struct file_operations dma_buf_fops = { .release = dma_buf_release, .mmap = dma_buf_mmap_internal, + .llseek = dma_buf_llseek, }; /* @@ -133,6 +160,7 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops, dmabuf->exp_name = exp_name; file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags); + file->f_mode |= FMODE_LSEEK; dmabuf->file = file;