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d="scan'208";a="502788500" Received: from unknown (HELO [10.239.154.46]) ([10.239.154.46]) by fmsmga006.fm.intel.com with ESMTP; 03 Sep 2020 23:08:53 -0700 Subject: Re: [PATCH] i2c: virtio: add a virtio i2c frontend driver To: Andy Shevchenko References: <0efc2605c8c06b4b1bf68cbad5536c4a900dc019.1599110284.git.jie.deng@intel.com> <20200903102008.GY1891694@smile.fi.intel.com> From: Jie Deng Message-ID: <71587fa1-ded8-2f96-378f-fc1ecc18a1a1@intel.com> Date: Fri, 4 Sep 2020 14:08:52 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.0.1 MIME-Version: 1.0 In-Reply-To: <20200903102008.GY1891694@smile.fi.intel.com> Content-Language: en-US Cc: Sergey.Semin@baikalelectronics.ru, bjorn.andersson@linaro.org, loic.poulain@linaro.org, yu1.wang@intel.com, mst@redhat.com, linux-kernel@vger.kernel.org, krzk@kernel.org, virtualization@lists.linux-foundation.org, wsa@kernel.org, wsa+renesas@sang-engineering.com, jarkko.nikula@linux.intel.com, linux-i2c@vger.kernel.org, rppt@kernel.org, shuo.a.liu@intel.com, tali.perry1@gmail.com, conghui.chen@intel.com, jdelvare@suse.de X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On 2020/9/3 18:20, Andy Shevchenko wrote: > On Thu, Sep 03, 2020 at 01:34:45PM +0800, Jie Deng wrote: >> Add an I2C bus driver for virtio para-virtualization. >> >> The controller can be emulated by the backend driver in >> any device model software by following the virtio protocol. >> >> This driver communicates with the backend driver through a >> virtio I2C message structure which includes following parts: >> >> - Header: i2c_msg addr, flags, len. >> - Data buffer: the pointer to the i2c msg data. >> - Status: the processing result from the backend. >> >> People may implement different backend drivers to emulate >> different controllers according to their needs. A backend >> example can be found in the device model of the open source >> project ACRN. For more information, please refer to >> https://projectacrn.org. >> >> The virtio device ID 34 is used for this I2C adpter since IDs >> before 34 have been reserved by other virtio devices. > Seems it's slightly different version to what I have reviewed internally. > My comments below. (I admit that some of them maybe new) > > ... Yeah... Some new devices have been added into the virtio spec during these days. >> +/** >> + * struct virtio_i2c_hdr - the virtio I2C message header structure >> + * @addr: i2c_msg addr, the slave address >> + * @flags: i2c_msg flags >> + * @len: i2c_msg len >> + */ >> +struct virtio_i2c_hdr { >> + __virtio16 addr; >> + __virtio16 flags; >> + __virtio16 len; >> +} __packed; > As Misha noticed and somewhere I saw 0-day reports these should be carefully > taken care of. > > ... Sure. Will fix these. >> +static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num) >> +{ >> + struct virtio_i2c *vi = i2c_get_adapdata(adap); >> + struct virtio_i2c_msg *vmsg_o, *vmsg_i; >> + struct virtqueue *vq = vi->vq; >> + unsigned long time_left; >> + int len, i, ret = 0; >> + >> + vmsg_o = kzalloc(sizeof(*vmsg_o), GFP_KERNEL); >> + if (!vmsg_o) >> + return -ENOMEM; >> + >> + mutex_lock(&vi->i2c_lock); >> + vmsg_o->buf = NULL; >> + for (i = 0; i < num; i++) { >> + ret = virtio_i2c_add_msg(vq, vmsg_o, &msgs[i]); >> + if (ret) { >> + dev_err(&adap->dev, "failed to add msg[%d] to virtqueue.\n", i); >> + goto err_unlock_free; > break; OK. >> + } >> + >> + virtqueue_kick(vq); >> + >> + time_left = wait_for_completion_timeout(&vi->completion, adap->timeout); >> + if (!time_left) { >> + dev_err(&adap->dev, "msg[%d]: addr=0x%x timeout.\n", i, msgs[i].addr); >> + ret = i; >> + goto err_unlock_free; > break; > > And so on. OK. >> + } >> + >> + vmsg_i = (struct virtio_i2c_msg *)virtqueue_get_buf(vq, &len); >> + if (vmsg_i) { >> + /* vmsg_i should point to the same address with vmsg_o */ >> + if (vmsg_i != vmsg_o) { >> + dev_err(&adap->dev, "msg[%d]: addr=0x%x virtqueue error.\n", >> + i, vmsg_i->hdr.addr); >> + ret = i; >> + goto err_unlock_free; >> + } >> + if (vmsg_i->status != VIRTIO_I2C_MSG_OK) { >> + dev_err(&adap->dev, "msg[%d]: addr=0x%x error=%d.\n", >> + i, vmsg_i->hdr.addr, vmsg_i->status); >> + ret = i; >> + goto err_unlock_free; >> + } >> + if ((vmsg_i->hdr.flags & I2C_M_RD) && vmsg_i->hdr.len) >> + memcpy(msgs[i].buf, vmsg_i->buf, vmsg_i->hdr.len); >> + >> + kfree(vmsg_i->buf); >> + vmsg_i->buf = NULL; >> + } >> + reinit_completion(&vi->completion); >> + } >> + if (i == num) >> + ret = num; > And this conditional seems a dup of the for-loop successfully iterating over > entire queue. You are right. We may save several lines of code by using "Return (ret<0) ? ret : i" at the end. >> +err_unlock_free: > Redundant. OK. >> + mutex_unlock(&vi->i2c_lock); >> + kfree(vmsg_o->buf); >> + kfree(vmsg_o); >> + return ret; >> +} > ... > >> + vi->adap.timeout = HZ / 10; > + Blank line. OK. >> + ret = i2c_add_adapter(&vi->adap); >> + if (ret) { >> + dev_err(&vdev->dev, "failed to add virtio-i2c adapter.\n"); >> + virtio_i2c_del_vqs(vdev); > Usually we do clean up followed by message. I will change the order. Thank you. >> + } >> + >> + return ret; > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization