termux-packages/packages/libusb/termux-usb-support.patch

--- libusb-1.0.27/libusb/os/linux_usbfs.c
+++ libusb-1.0.27.mod/libusb/os/linux_usbfs.c
@@ -26,6 +26,7 @@
 #include "linux_usbfs.h"
 
 #include <alloca.h>
+#include <bits/fcntl.h>
 #include <ctype.h>
 #include <dirent.h>
 #include <errno.h>
@@ -74,6 +75,7 @@
 
 #define USBDEV_PATH		"/dev"
 #define USB_DEVTMPFS_PATH	"/dev/bus/usb"
+#define TERMUX_USB_ENV		"TERMUX_USB_FD"
 
 /* use usbdev*.* device names in /dev instead of the usbfs bus directories */
 static int usbdev_names = 0;
@@ -105,6 +107,8 @@
 static int linux_default_scan_devices(struct libusb_context *ctx);
 #endif
 
+static int linux_termux_scan_devices(struct libusb_context *ctx);
+
 struct kernel_version {
 	int major;
 	int minor;
@@ -127,6 +131,7 @@
 	size_t descriptors_len;
 	struct config_descriptor *config_descriptors;
 	int active_config; /* cache val for !sysfs_available  */
+	int termux_fd;
 };
 
 struct linux_device_handle_priv {
@@ -188,6 +193,24 @@
 	char path[24];
 	int fd;
 
+	struct linux_device_priv *priv = usbi_get_device_priv(dev);
+
+	if ((fd = priv->termux_fd) != -1) {
+		/* The returned fd (from this function) might gets closed at some
+		 * point in the future when the user close the handle
+		 * Avoid touching the fd given by Android since we might want to close
+		 * and reopen the device again */
+		if ((fd = dup(priv->termux_fd)) == -1) {
+			usbi_err(ctx, "unable to duplicate termux usb fd: %s", strerror(errno));
+			return LIBUSB_ERROR_IO;
+		}
+		/* Android gives fd with O_RDWR by default, and changing the mode
+		 * of an fd is not possible at the moment */
+		usbi_info(ctx, "setting fd mode for termux supplied usb device is unsupported, the fd will have mode O_RDWR instead");
+
+		return fd;
+	}
+
 	if (usbdev_names)
 		snprintf(path, sizeof(path), USBDEV_PATH "/usbdev%u.%u",
 			dev->bus_number, dev->device_address);
@@ -458,12 +481,18 @@
 
 	usbi_mutex_static_lock(&linux_hotplug_lock);
 
+	if (getenv(TERMUX_USB_ENV)) {
+		ret = linux_termux_scan_devices(ctx);
+		goto out;
+	}
+
 #if defined(HAVE_LIBUDEV)
 	ret = linux_udev_scan_devices(ctx);
 #else
 	ret = linux_default_scan_devices(ctx);
 #endif
 
+out:
 	usbi_mutex_static_unlock(&linux_hotplug_lock);
 
 	return ret;
@@ -916,6 +945,8 @@
 	int fd, speed, r;
 	ssize_t nb;
 
+	priv->termux_fd = -1;
+
 	dev->bus_number = busnum;
 	dev->device_address = devaddr;
 
@@ -1328,6 +1359,74 @@
 }
 #endif
 
+static int linux_termux_get_devinfo(int fd, uint8_t *busnum, uint8_t *devaddr)
+{
+	char proc_path[PATH_MAX], usbfs_path[PATH_MAX];
+
+	snprintf(proc_path, PATH_MAX, "/proc/self/fd/%u", fd);
+	if (readlink(proc_path, usbfs_path, PATH_MAX) < 0 ||
+		strncmp("/dev/bus/usb/", usbfs_path, 12)) {
+		return LIBUSB_ERROR_IO;
+	}
+
+	if (sscanf(usbfs_path, "/dev/bus/usb/%hhu/%hhu", busnum, devaddr) != 2)
+		return LIBUSB_ERROR_IO;
+
+	return LIBUSB_SUCCESS;
+}
+
+static int linux_termux_scan_devices(struct libusb_context *ctx)
+{
+	struct libusb_device *dev;
+	struct linux_device_priv *priv;
+	uint8_t busnum, devaddr;
+	unsigned long session_id;
+	char *envval, *envval_end;
+	int fd, r;
+
+	envval = getenv(TERMUX_USB_ENV);
+
+	assert(envval);
+
+	errno = 0;
+	fd = strtol(envval, &envval_end, 10);
+	if (*envval == '\0' || *envval_end != '\0' || errno || fd < 0) {
+		usbi_err(ctx, "invalid usb fd in TERMUX_USB_FD");
+		return LIBUSB_ERROR_NO_DEVICE;
+	}
+
+	r = linux_termux_get_devinfo(fd, &busnum, &devaddr);
+	if (r < 0) {
+		usbi_err(ctx, "unable to get device info from fd %d", fd);
+		return r;
+	}
+
+	session_id = busnum << 8 | devaddr;
+	usbi_dbg(ctx, "allocating new device for %u/%u (session %lu)",
+		 busnum, devaddr, session_id);
+	dev = usbi_alloc_device(ctx, session_id);
+	if (!dev)
+		return LIBUSB_ERROR_NO_MEM;
+
+	r = initialize_device(dev, busnum, devaddr, NULL, fd);
+	if (r < 0)
+		goto out;
+	r = usbi_sanitize_device(dev);
+	if (r < 0)
+		goto out;
+
+	priv = usbi_get_device_priv(dev);
+	priv->termux_fd = fd;
+
+out:
+	if (r < 0)
+		libusb_unref_device(dev);
+	else
+		usbi_connect_device(dev);
+
+	return r;
+}
+
 static int initialize_handle(struct libusb_device_handle *handle, int fd)
 {
 	struct linux_device_handle_priv *hpriv = usbi_get_device_handle_priv(handle);