From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 02FF1C11F64 for ; Thu, 1 Jul 2021 06:11:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BB8F361483 for ; Thu, 1 Jul 2021 06:10:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233878AbhGAGNZ (ORCPT ); Thu, 1 Jul 2021 02:13:25 -0400 Received: from mga02.intel.com ([134.134.136.20]:1867 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232797AbhGAGNZ (ORCPT ); Thu, 1 Jul 2021 02:13:25 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10031"; a="195638111" X-IronPort-AV: E=Sophos;i="5.83,313,1616482800"; d="scan'208";a="195638111" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Jun 2021 23:10:52 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.83,313,1616482800"; d="scan'208";a="420285841" Received: from dengjie-mobl1.ccr.corp.intel.com (HELO [10.239.154.58]) ([10.239.154.58]) by fmsmga007.fm.intel.com with ESMTP; 30 Jun 2021 23:10:48 -0700 Subject: Re: [PATCH v11] i2c: virtio: add a virtio i2c frontend driver To: Viresh Kumar Cc: linux-i2c@vger.kernel.org, virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, wsa@kernel.org, wsa+renesas@sang-engineering.com, mst@redhat.com, arnd@arndb.de, jasowang@redhat.com, andriy.shevchenko@linux.intel.com, yu1.wang@intel.com, shuo.a.liu@intel.com, conghui.chen@intel.com, stefanha@redhat.com References: <510c876952efa693339ab0d6cc78ba7be9ef6897.1625104206.git.jie.deng@intel.com> <20210701040436.p7kega6rzeqz5tlm@vireshk-i7> From: Jie Deng Message-ID: Date: Thu, 1 Jul 2021 14:10:48 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.10.0 MIME-Version: 1.0 In-Reply-To: <20210701040436.p7kega6rzeqz5tlm@vireshk-i7> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-i2c@vger.kernel.org On 2021/7/1 12:04, Viresh Kumar wrote: > On 01-07-21, 11:24, Jie Deng wrote: >> Changes v10 -> v11 >> - Remove vi->adap.class = I2C_CLASS_DEPRECATED. >> - Use #ifdef CONFIG_PM_SLEEP to replace the "__maybe_unused". >> - Remove "struct mutex lock" in "struct virtio_i2c". >> - Support zero-length request. >> - Remove unnecessary logs. >> - Remove vi->adap.timeout = HZ / 10, just use the default value. >> - Use BIT(0) to define VIRTIO_I2C_FLAGS_FAIL_NEXT. >> - Add the virtio_device index to adapter's naming mechanism. > Thanks Jie. > > I hope you are going to send a fix for specification as well (for the > zero-length request) ? Yes. I will send that fix once this patch get merged. > >> diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c >> +static int virtio_i2c_send_reqs(struct virtqueue *vq, >> + struct virtio_i2c_req *reqs, >> + struct i2c_msg *msgs, int nr) >> +{ >> + struct scatterlist *sgs[3], out_hdr, msg_buf, in_hdr; >> + int i, outcnt, incnt, err = 0; >> + >> + for (i = 0; i < nr; i++) { >> + /* >> + * Only 7-bit mode supported for this moment. For the address format, >> + * Please check the Virtio I2C Specification. >> + */ >> + reqs[i].out_hdr.addr = cpu_to_le16(msgs[i].addr << 1); >> + >> + if (i != nr - 1) >> + reqs[i].out_hdr.flags = cpu_to_le32(VIRTIO_I2C_FLAGS_FAIL_NEXT); >> + >> + outcnt = incnt = 0; >> + sg_init_one(&out_hdr, &reqs[i].out_hdr, sizeof(reqs[i].out_hdr)); >> + sgs[outcnt++] = &out_hdr; >> + >> + reqs[i].buf = i2c_get_dma_safe_msg_buf(&msgs[i], 1); >> + if (!reqs[i].buf) >> + break; >> + >> + sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len); > The len can be zero here for zero-length transfers. > >> + >> + if (msgs[i].flags & I2C_M_RD) >> + sgs[outcnt + incnt++] = &msg_buf; >> + else >> + sgs[outcnt++] = &msg_buf; >> + >> + sg_init_one(&in_hdr, &reqs[i].in_hdr, sizeof(reqs[i].in_hdr)); >> + sgs[outcnt + incnt++] = &in_hdr; > Why are we still sending the msg_buf if the length is 0? Sending the > buffer makes sense if you have some data to send, but otherwise it is > just an extra sg element, which isn't required to be sent. I think a fixed number of sgs will make things easier to develop backend. If you prefer to parse the number of descriptors instead of using the msg length to distinguish the zero-length request from other requests, I'm OK to set a limit. if (!msgs[i].len) {     sg_init_one(&msg_buf, reqs[i].buf, msgs[i].len);     if (msgs[i].flags & I2C_M_RD)         sgs[outcnt + incnt++] = &msg_buf;     else         sgs[outcnt++] = &msg_buf; } > >> +#ifdef CONFIG_PM_SLEEP >> +static int virtio_i2c_freeze(struct virtio_device *vdev) >> +{ >> + virtio_i2c_del_vqs(vdev); >> + return 0; >> +} >> + >> +static int virtio_i2c_restore(struct virtio_device *vdev) >> +{ >> + return virtio_i2c_setup_vqs(vdev->priv); >> +} >> +#endif >> + >> +static struct virtio_driver virtio_i2c_driver = { >> + .id_table = id_table, >> + .probe = virtio_i2c_probe, >> + .remove = virtio_i2c_remove, >> + .driver = { >> + .name = "i2c_virtio", >> + }, >> +#ifdef CONFIG_PM_SLEEP > You could avoid this pair of ifdef by creating dummy versions of below > routines for !CONFIG_PM_SLEEP case. Up to you. Thank you. I'd like to keep the same.