From: Alan Stern Date: Sun, 2 Jul 2006 02:06:36 +0000 (-0400) Subject: usb-skeleton: don't submit URBs after disconnection X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=121e287cb554f3d3402c85a1950d852691b08f5c;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git usb-skeleton: don't submit URBs after disconnection This patch (as712b) is a slight revision of one submitted earlier. It fixes the usb-skeleton example driver so that it won't try to submit URBs after skel_disconnect() has returned. This could cause errors, if the driver was unbound and then a different driver was bound to the device. It also fixes a couple of small bugs in the skel_write() routine. The revised patch uses a slightly different test, suggested by Dave Brownell, for determining whether to free a transfer buffer. It's a little clearer than the earlier version. Signed-off-by: Alan Stern Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/usb/usb-skeleton.c b/drivers/usb/usb-skeleton.c index b362039792b3..33f0e81c58d3 100644 --- a/drivers/usb/usb-skeleton.c +++ b/drivers/usb/usb-skeleton.c @@ -1,5 +1,5 @@ /* - * USB Skeleton driver - 2.0 + * USB Skeleton driver - 2.1 * * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com) * @@ -8,8 +8,7 @@ * published by the Free Software Foundation, version 2. * * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c - * but has been rewritten to be easy to read and use, as no locks are now - * needed anymore. + * but has been rewritten to be easier to read and use. * */ @@ -21,6 +20,7 @@ #include #include #include +#include /* Define these values to match your devices */ @@ -52,6 +52,7 @@ struct usb_skel { __u8 bulk_in_endpointAddr; /* the address of the bulk in endpoint */ __u8 bulk_out_endpointAddr; /* the address of the bulk out endpoint */ struct kref kref; + struct mutex io_mutex; /* synchronize I/O with disconnect */ }; #define to_skel_dev(d) container_of(d, struct usb_skel, kref) @@ -119,7 +120,13 @@ static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t * int bytes_read; dev = (struct usb_skel *)file->private_data; - + + mutex_lock(&dev->io_mutex); + if (!dev->interface) { /* disconnect() was called */ + retval = -ENODEV; + goto exit; + } + /* do a blocking bulk read to get data from the device */ retval = usb_bulk_msg(dev->udev, usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr), @@ -135,6 +142,8 @@ static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t * retval = bytes_read; } +exit: + mutex_unlock(&dev->io_mutex); return retval; } @@ -179,6 +188,12 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou goto exit; } + mutex_lock(&dev->io_mutex); + if (!dev->interface) { /* disconnect() was called */ + retval = -ENODEV; + goto error; + } + /* create a urb, and a buffer for it, and copy the data to the urb */ urb = usb_alloc_urb(0, GFP_KERNEL); if (!urb) { @@ -213,13 +228,18 @@ static ssize_t skel_write(struct file *file, const char *user_buffer, size_t cou /* release our reference to this urb, the USB core will eventually free it entirely */ usb_free_urb(urb); -exit: + mutex_unlock(&dev->io_mutex); return writesize; error: - usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma); - usb_free_urb(urb); + if (urb) { + usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma); + usb_free_urb(urb); + } + mutex_unlock(&dev->io_mutex); up(&dev->limit_sem); + +exit: return retval; } @@ -258,6 +278,7 @@ static int skel_probe(struct usb_interface *interface, const struct usb_device_i } kref_init(&dev->kref); sema_init(&dev->limit_sem, WRITES_IN_FLIGHT); + mutex_init(&dev->io_mutex); dev->udev = usb_get_dev(interface_to_usbdev(interface)); dev->interface = interface; @@ -334,6 +355,11 @@ static void skel_disconnect(struct usb_interface *interface) /* give back our minor */ usb_deregister_dev(interface, &skel_class); + /* prevent more I/O from starting */ + mutex_lock(&dev->io_mutex); + dev->interface = NULL; + mutex_unlock(&dev->io_mutex); + unlock_kernel(); /* decrement our usage count */