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authorSudip Mukherjee <sudipm.mukherjee@gmail.com>2019-10-16 17:45:39 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2019-11-13 14:09:48 +0300
commit231ec2f24dad18d021b361045bbd618ba62a274e (patch)
tree942b7ee1db2fd7d10c180a58367780ce0a4dd28e /drivers/parport
parente962cd9cf9cfb1f5db6bbad6a6470e5ccf56e290 (diff)
downloadlinux-231ec2f24dad18d021b361045bbd618ba62a274e.tar.xz
parport: load lowlevel driver if ports not found
Usually all the distro will load the parport low level driver as part of their initialization. But we can get into a situation where all the parallel port drivers are built as module and we unload all the modules at a later time. Then if we just do "modprobe parport" it will only load the parport module and will not load the low level driver which will actually register the ports. So, check the bus if there is any parport registered, if not, load the low level driver. We can get into the above situation with all distro but only Suse has setup the alias for "parport_lowlevel" and so it only works in Suse. Users of Debian based distro will need to load the lowlevel module manually. Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com> Link: https://lore.kernel.org/r/20191016144540.18810-3-sudipm.mukherjee@gmail.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/parport')
-rw-r--r--drivers/parport/share.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/drivers/parport/share.c b/drivers/parport/share.c
index 96538b7975e5..d6920ebeabcd 100644
--- a/drivers/parport/share.c
+++ b/drivers/parport/share.c
@@ -230,6 +230,18 @@ static int port_check(struct device *dev, void *dev_drv)
return 0;
}
+/*
+ * Iterates through all the devices connected to the bus and return 1
+ * if the device is a parallel port.
+ */
+
+static int port_detect(struct device *dev, void *dev_drv)
+{
+ if (is_parport(dev))
+ return 1;
+ return 0;
+}
+
/**
* parport_register_driver - register a parallel port device driver
* @drv: structure describing the driver
@@ -279,6 +291,15 @@ int __parport_register_driver(struct parport_driver *drv, struct module *owner,
if (ret)
return ret;
+ /*
+ * check if bus has any parallel port registered, if
+ * none is found then load the lowlevel driver.
+ */
+ ret = bus_for_each_dev(&parport_bus_type, NULL, NULL,
+ port_detect);
+ if (!ret)
+ get_lowlevel_driver();
+
mutex_lock(&registration_lock);
if (drv->match_port)
bus_for_each_dev(&parport_bus_type, NULL, drv,