Messages in this thread | | | Subject | Re: [PATCH v6 4/4] bus: mhi: Add userspace client interface driver | From | Hemant Kumar <> | Date | Wed, 23 Sep 2020 11:17:30 -0700 |
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Hi Jeff,
On 9/18/20 1:08 PM, Jeffrey Hugo wrote: > On 9/16/2020 1:56 PM, Hemant Kumar wrote: >> This MHI client driver allows userspace clients to transfer >> raw data between MHI device and host using standard file operations. >> Device file node is created with format >> >> /dev/mhi_<controller_name>_<mhi_device_name> >> >> Currently it supports LOOPBACK channel. >> >> Signed-off-by: Hemant Kumar <hemantk@codeaurora.org> ... ... >> + >> +static ssize_t mhi_uci_write(struct file *file, >> + const char __user *buf, >> + size_t count, >> + loff_t *offp) >> +{ >> + struct uci_dev *udev = file->private_data; >> + struct mhi_device *mhi_dev = udev->mhi_dev; >> + struct device *dev = &mhi_dev->dev; >> + struct uci_chan *uchan = &udev->ul_chan; >> + size_t bytes_xfered = 0; >> + int ret, nr_avail = 0; >> + >> + if (!buf || !count) >> + return -EINVAL; >> + >> + /* confirm channel is active */ >> + mutex_lock(&udev->lock); >> + if (!udev->enabled) { >> + ret = -ENODEV; >> + goto err_mtx_unlock; >> + } >> + >> + dev_dbg(dev, "%s: to xfer: %lu bytes\n", __func__, count); >> + >> + while (count) { >> + size_t xfer_size; >> + void *kbuf; >> + enum mhi_flags flags; >> + >> + mutex_unlock(&udev->lock); >> + /* wait for free descriptors */ >> + ret = wait_event_interruptible(uchan->wq, >> + (!udev->enabled) || >> + (nr_avail = mhi_get_no_free_descriptors(mhi_dev, >> + DMA_TO_DEVICE)) > 0); >> + >> + mutex_lock(&udev->lock); > > It feels like there is a race here. What if we wait because there are > no free descriptors, one becomes available, but someone else manages to > grab the mutex before we do, and consume it? mhi_queue_buf() will fail > later on, and I don't think thats intended. I agree Jeff, one option i can think of having separate read and write lock so that writer can hold lock if TREs are not available but reader can continue. > >> + if (ret == -ERESTARTSYS) { >> + dev_dbg(dev, "Exit signal caught for node\n"); >> + goto err_mtx_unlock; >> + } >> + >> + if (!udev->enabled) { >> + ret = -ENODEV; >> + goto err_mtx_unlock; >> + } >> + >> + xfer_size = min_t(size_t, count, udev->mtu); >> + kbuf = kmalloc(xfer_size, GFP_KERNEL); >> + if (!kbuf) { >> + ret = -ENOMEM; >> + goto err_mtx_unlock; >> + } >> + >> + ret = copy_from_user(kbuf, buf, xfer_size); >> + if (ret) { >> + kfree(kbuf); >> + ret = -EFAULT; >> + goto err_mtx_unlock; >> + } >> + >> + /* if ring is full after this force EOT */ >> + if (nr_avail > 1 && (count - xfer_size)) >> + flags = MHI_CHAIN; >> + else >> + flags = MHI_EOT; >> + >> + if (udev->enabled) >> + ret = mhi_queue_buf(mhi_dev, DMA_TO_DEVICE, kbuf, >> + xfer_size, flags); >> + else >> + ret = -ENODEV; >> + >> + if (ret) { >> + kfree(kbuf); >> + goto err_mtx_unlock; >> + } >> + >> + bytes_xfered += xfer_size; >> + count -= xfer_size; >> + buf += xfer_size; >> + } >> + >> + mutex_unlock(&udev->lock); >> + dev_dbg(dev, "%s: bytes xferred: %lu\n", __func__, bytes_xfered); >> + >> + return bytes_xfered; >> + >> +err_mtx_unlock: >> + mutex_unlock(&udev->lock); >> + >> + return ret; >> +} >> + >> +static ssize_t mhi_uci_read(struct file *file, >> + char __user *buf, >> + size_t count, >> + loff_t *ppos) >> +{ >> + struct uci_dev *udev = file->private_data; >> + struct mhi_device *mhi_dev = udev->mhi_dev; >> + struct uci_chan *uchan = &udev->dl_chan; >> + struct device *dev = &mhi_dev->dev; >> + struct uci_buf *ubuf; >> + char *ptr; >> + size_t to_copy; >> + int ret = 0; >> + >> + if (!buf) >> + return -EINVAL; >> + >> + mutex_lock(&udev->lock); >> + /* confirm channel is active */ >> + if (!udev->enabled) { >> + ret = -ENODEV; >> + goto err_mtx_unlock; >> + } >> + >> + spin_lock_bh(&uchan->lock); >> + /* No data available to read, wait */ >> + if (!uchan->cur_buf && list_empty(&uchan->pending)) { >> + dev_dbg(dev, "No data available to read waiting\n"); >> + >> + spin_unlock_bh(&uchan->lock); >> + mutex_unlock(&udev->lock); >> + ret = wait_event_interruptible(uchan->wq, >> + (!udev->enabled || >> + !list_empty(&uchan->pending))); >> + >> + mutex_lock(&udev->lock); >> + if (ret == -ERESTARTSYS) { >> + dev_dbg(dev, "Exit signal caught for node\n"); >> + goto err_mtx_unlock; >> + } >> + >> + if (!udev->enabled) { >> + ret = -ENODEV; >> + goto err_mtx_unlock; >> + } >> + spin_lock_bh(&uchan->lock); >> + } >> + >> + /* new read, get the next descriptor from the list */ >> + if (!uchan->cur_buf) { >> + ubuf = list_first_entry_or_null(&uchan->pending, >> + struct uci_buf, node); >> + if (!ubuf) { >> + ret = -EIO; >> + goto err_spin_unlock; >> + } >> + >> + list_del(&ubuf->node); >> + uchan->cur_buf = ubuf; >> + uchan->rx_size = ubuf->len; >> + dev_dbg(dev, "Got pkt of size: %zu\n", uchan->rx_size); >> + } >> + >> + ubuf = uchan->cur_buf; >> + >> + /* Copy the buffer to user space */ >> + to_copy = min_t(size_t, count, uchan->rx_size); >> + ptr = ubuf->data + (ubuf->len - uchan->rx_size); >> + spin_unlock_bh(&uchan->lock); >> + >> + ret = copy_to_user(buf, ptr, to_copy); >> + if (ret) { >> + ret = -EFAULT; >> + goto err_mtx_unlock; >> + } >> + >> + spin_lock_bh(&uchan->lock); >> + >> + dev_dbg(dev, "Copied %lu of %lu bytes\n", to_copy, uchan->rx_size); >> + uchan->rx_size -= to_copy; >> + >> + /* we finished with this buffer, queue it back to hardware */ >> + if (!uchan->rx_size) { >> + uchan->cur_buf = NULL; >> + >> + if (udev->enabled) >> + ret = mhi_queue_buf(mhi_dev, DMA_FROM_DEVICE, >> + ubuf->data, >> + udev->actual_mtu, MHI_EOT); >> + else >> + ret = -ENODEV; >> + >> + if (ret) { >> + dev_err(dev, "Failed to recycle element: %d\n", ret); >> + kfree(ubuf->data); >> + goto err_spin_unlock; >> + } >> + } >> + spin_unlock_bh(&uchan->lock); >> + mutex_unlock(&udev->lock); >> + >> + dev_dbg(dev, "%s: Returning %lu bytes\n", __func__, to_copy); >> + >> + return to_copy; >> + >> +err_spin_unlock: >> + spin_unlock_bh(&uchan->lock); >> +err_mtx_unlock: >> + mutex_unlock(&udev->lock); >> + return ret; >> +} >> + >> +static int mhi_uci_open(struct inode *inode, struct file *filp) >> +{ >> + struct uci_dev *udev = NULL; >> + unsigned int minor = iminor(inode); >> + int ret = -EIO; >> + struct uci_buf *buf_itr, *tmp; >> + struct uci_chan *dl_chan; >> + struct mhi_device *mhi_dev; >> + struct device *dev; >> + >> + mutex_lock(&uci_idr_mutex); >> + udev = idr_find(&uci_idr, minor); >> + mutex_unlock(&uci_idr_mutex); >> + if (!udev) { >> + pr_err("uci dev: minor %d not found\n", minor); >> + ret = -ENODEV; >> + goto error_no_dev; >> + } >> + >> + kref_get(&udev->ref_count); >> + >> + mhi_dev = udev->mhi_dev; > > mhi_dev never gets used. You could use it down at the > prepare_for_transfer, but you don't. Might as well just remove this > from the stack. this was done to pass dev pointer instead of udev->mhi_dev->dev. > >> + dev = &mhi_dev->dev; >> + >> + mutex_lock(&udev->lock); >> + if (kref_read(&udev->ref_count) > 2) { >> + dev_dbg(dev, "Node already opened\n"); >> + goto exit_uci_open; >> + } >> + >> + if (!udev->enabled) { >> + dev_info(dev, "Node exists, but is not in active state!\n"); >> + goto error_open_chan; >> + } >> + >> + dev_dbg(dev, "Starting channel\n"); >> + ret = mhi_prepare_for_transfer(udev->mhi_dev); >> + if (ret) { >> + dev_err(dev, "Error starting transfer channels\n"); >> + goto error_open_chan; >> + } >> + >> + ret = mhi_queue_inbound(udev); >> + if (ret) >> + goto error_rx_queue; >> + >> +exit_uci_open: >> + filp->private_data = udev; >> + mutex_unlock(&udev->lock); >> + >> + return 0; >> + >> +error_rx_queue: >> + dl_chan = &udev->dl_chan; >> + mhi_unprepare_from_transfer(udev->mhi_dev); >> + list_for_each_entry_safe(buf_itr, tmp, &dl_chan->pending, node) { >> + list_del(&buf_itr->node); >> + kfree(buf_itr->data); >> + } >> +error_open_chan: >> + mutex_unlock(&udev->lock); >> + kref_put(&udev->ref_count, mhi_uci_dev_release); >> +error_no_dev: >> + return ret; >> +} >> + >> +static const struct file_operations mhidev_fops = { >> + .owner = THIS_MODULE, >> + .open = mhi_uci_open, >> + .release = mhi_uci_release, >> + .read = mhi_uci_read, >> + .write = mhi_uci_write, >> + .poll = mhi_uci_poll, >> +}; >> + >> +static void mhi_ul_xfer_cb(struct mhi_device *mhi_dev, >> + struct mhi_result *mhi_result) >> +{ >> + struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev); >> + struct uci_chan *uchan = &udev->ul_chan; >> + struct device *dev = &mhi_dev->dev; >> + >> + dev_dbg(dev, "status: %d xfer_len: %zu\n", >> + mhi_result->transaction_status, mhi_result->bytes_xferd); >> + >> + kfree(mhi_result->buf_addr); >> + >> + if (!mhi_result->transaction_status) >> + wake_up(&uchan->wq); >> +} >> + >> +static void mhi_dl_xfer_cb(struct mhi_device *mhi_dev, >> + struct mhi_result *mhi_result) >> +{ >> + struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev); >> + struct uci_chan *uchan = &udev->dl_chan; >> + struct device *dev = &mhi_dev->dev; >> + struct uci_buf *buf; >> + >> + dev_dbg(dev, "status: %d receive_len: %zu\n", >> + mhi_result->transaction_status, mhi_result->bytes_xferd); >> + >> + if (mhi_result->transaction_status == -ENOTCONN) { >> + kfree(mhi_result->buf_addr); >> + return; >> + } >> + >> + spin_lock_bh(&uchan->lock); >> + buf = mhi_result->buf_addr + udev->actual_mtu; >> + buf->data = mhi_result->buf_addr; >> + buf->len = mhi_result->bytes_xferd; >> + list_add_tail(&buf->node, &uchan->pending); >> + spin_unlock_bh(&uchan->lock); >> + >> + wake_up(&uchan->wq); >> +} >> + >> +static int mhi_uci_probe(struct mhi_device *mhi_dev, >> + const struct mhi_device_id *id) >> +{ >> + struct uci_dev *udev; >> + struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl; >> + struct device *dev; >> + int index, dir; >> + >> + udev = kzalloc(sizeof(*udev), GFP_KERNEL); > > What if you defer creating the udev until the first open(), and tie the > xfer prepare state to the ref count of the udev instance? With current implementation udev and minor are mapped using idr_alloc. i was thinking about another option of adding kref for uci_chann object to take care of channel and buffer ref count. > >> + if (!udev) >> + return -ENOMEM; >> + >> + kref_init(&udev->ref_count); >> + mutex_init(&udev->lock); >> + udev->mhi_dev = mhi_dev; >> + >> + mutex_lock(&udev->lock); >> + >> + mutex_lock(&uci_idr_mutex); >> + index = idr_alloc(&uci_idr, udev, 0, MAX_UCI_MINORS, GFP_KERNEL); >> + mutex_unlock(&uci_idr_mutex); >> + if (index < 0) { >> + mutex_unlock(&udev->lock); >> + kfree(udev); >> + return index; >> + } >> + >> + udev->minor = index; >> + >> + /* create device file node >> /dev/mhi_<cntrl_dev_name>_<mhi_dev_name> */ >> + dev = device_create(uci_dev_class, &mhi_dev->dev, >> + MKDEV(uci_dev_major, index), udev, >> + DEVICE_NAME "_%s_%s", > > DEVICE_NAME is only used here. Doesn't seem like having a macro is > providing much value. I suggest just inlining the value. > >> + dev_name(mhi_cntrl->cntrl_dev), mhi_dev->name); >> + if (IS_ERR(dev)) { >> + mutex_lock(&uci_idr_mutex); >> + idr_remove(&uci_idr, udev->minor); >> + mutex_unlock(&uci_idr_mutex); >> + mutex_unlock(&udev->lock); >> + kfree(udev); >> + return PTR_ERR(dev); >> + } >> + >> + for (dir = 0; dir < 2; dir++) { >> + struct uci_chan *uchan = (dir) ? >> + &udev->ul_chan : &udev->dl_chan; >> + spin_lock_init(&uchan->lock); >> + init_waitqueue_head(&uchan->wq); >> + INIT_LIST_HEAD(&uchan->pending); >> + } >> + >> + udev->mtu = min_t(size_t, id->driver_data, MHI_MAX_MTU); >> + udev->actual_mtu = udev->mtu - sizeof(struct uci_buf); > > "mtu" vs "actual_mtu" seems to be very confusing. To start, why not > "tx_mtu" and "rx_mtu"? But going from there, why have different mtus > for tx and rx? Why not just increase the rx allocations by the required > "header" (struct uci_buf) as needed to keep symetry? in past we had issues with order of 3 allocation failures for bigger mtu size, so we decided to use memory within the mtu buffer. i can add tx_mtu and rx_mtu if that makes it clear. > >> + dev_set_drvdata(&mhi_dev->dev, udev); >> + udev->enabled = true; >> + >> + mutex_unlock(&udev->lock); >> + >> + dev_info(&mhi_dev->dev, "probed uci dev: minor %d\n", index); >> + >> + return 0; >> +}; >> + >> +static void mhi_uci_remove(struct mhi_device *mhi_dev) >> +{ >> + struct uci_dev *udev = dev_get_drvdata(&mhi_dev->dev); >> + >> + mutex_lock(&udev->lock); >> + >> + /* disable the node */ >> + udev->enabled = false; >> + >> + wake_up(&udev->dl_chan.wq); >> + wake_up(&udev->ul_chan.wq); >> + >> + /* delete the node to prevent new opens */ >> + device_destroy(uci_dev_class, MKDEV(uci_dev_major, udev->minor)); >> + >> + mutex_lock(&uci_idr_mutex); >> + idr_remove(&uci_idr, udev->minor); >> + mutex_unlock(&uci_idr_mutex); >> + >> + mutex_unlock(&udev->lock); >> + >> + kref_put(&udev->ref_count, mhi_uci_dev_release); >> +} >> + >> +/* .driver_data stores max mtu */ >> +static const struct mhi_device_id mhi_uci_match_table[] = { >> + { .chan = "LOOPBACK", .driver_data = 0x1000}, >> + {}, >> +}; >> +MODULE_DEVICE_TABLE(mhi, mhi_uci_match_table); >> + >> +static struct mhi_driver mhi_uci_driver = { >> + .id_table = mhi_uci_match_table, >> + .remove = mhi_uci_remove, >> + .probe = mhi_uci_probe, >> + .ul_xfer_cb = mhi_ul_xfer_cb, >> + .dl_xfer_cb = mhi_dl_xfer_cb, >> + .driver = { >> + .name = MHI_UCI_DRIVER_NAME, >> + }, >> +}; >> + >> +static int mhi_uci_init(void) >> +{ >> + int ret; >> + >> + ret = register_chrdev(0, MHI_UCI_DRIVER_NAME, &mhidev_fops); >> + if (ret < 0) >> + return ret; >> + >> + uci_dev_major = ret; >> + uci_dev_class = class_create(THIS_MODULE, MHI_UCI_DRIVER_NAME); >> + if (IS_ERR(uci_dev_class)) { >> + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME); >> + return -ENODEV; >> + } >> + >> + ret = mhi_driver_register(&mhi_uci_driver); >> + if (ret) { >> + class_destroy(uci_dev_class); >> + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME); >> + } >> + >> + return ret; >> +} >> + >> +static void __exit mhi_uci_exit(void) >> +{ >> + mhi_driver_unregister(&mhi_uci_driver); >> + class_destroy(uci_dev_class); >> + unregister_chrdev(uci_dev_major, MHI_UCI_DRIVER_NAME); > > I think you need an idr_destroy() of uci_idr here. Done. > >> +} >> + >> +module_init(mhi_uci_init); >> +module_exit(mhi_uci_exit); >> +MODULE_LICENSE("GPL v2"); >> +MODULE_DESCRIPTION("MHI UCI Driver"); >> >
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