Re: [PATCH 03/10] bus/fsl-mc: add support for 'driver_override' in the mc-bus

From: Diana Craciun OSS
Date: Thu Apr 09 2020 - 07:14:36 EST


On 3/23/2020 2:30 PM, Laurentiu Tudor wrote:

On 3/19/2020 5:40 PM, Diana Craciun wrote:
From: Bharat Bhushan <Bharat.Bhushan@xxxxxxx>

This patch is required for vfio-fsl-mc meta driver to successfully bind
layerscape container devices for device passthrough. This patch adds
a mechanism to allow a layerscape device to specify a driver rather than
a layerscape driver provide a device match.

Example to allow a device (dprc.1) to specifically bind
with driver (vfio-fsl-mc):-
- echo vfio-fsl-mc > /sys/bus/fsl-mc/devices/dprc.1/driver_override
- echo dprc.1 > /sys/bus/fsl-mc/drivers/fsl_mc_dprc/unbind
- echo dprc.1 > /sys/bus/fsl-mc/drivers/vfio-fsl-mc/bind

Signed-off-by: Bharat Bhushan <Bharat.Bhushan@xxxxxxx>
Signed-off-by: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
Signed-off-by: Diana Craciun <diana.craciun@xxxxxxxxxxx>
---
drivers/bus/fsl-mc/fsl-mc-bus.c | 54 +++++++++++++++++++++++++++++++++
include/linux/fsl/mc.h | 1 +
2 files changed, 55 insertions(+)

diff --git a/drivers/bus/fsl-mc/fsl-mc-bus.c b/drivers/bus/fsl-mc/fsl-mc-bus.c
index c78d10ea641f..baf8259262a9 100644
--- a/drivers/bus/fsl-mc/fsl-mc-bus.c
+++ b/drivers/bus/fsl-mc/fsl-mc-bus.c
@@ -3,6 +3,7 @@
* Freescale Management Complex (MC) bus driver
*
* Copyright (C) 2014-2016 Freescale Semiconductor, Inc.
+ * Copyright 2019-2020 NXP
* Author: German Rivera <German.Rivera@xxxxxxxxxxxxx>
*
*/
@@ -83,6 +84,12 @@ static int fsl_mc_bus_match(struct device *dev, struct device_driver *drv)
struct fsl_mc_driver *mc_drv = to_fsl_mc_driver(drv);
bool found = false;
+ /* When driver_override is set, only bind to the matching driver */
+ if (mc_dev->driver_override) {
+ found = !strcmp(mc_dev->driver_override, mc_drv->driver.name);
I think we can use sysfs_streq() here and ...

I would prefer to maintain consistency with other buses and store the driver_override string without the terminating newline.



+ goto out;
+ }
+
if (!mc_drv->match_id_table)
goto out;
@@ -147,8 +154,52 @@ static ssize_t modalias_show(struct device *dev, struct device_attribute *attr,
}
static DEVICE_ATTR_RO(modalias);
+static ssize_t driver_override_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
+ const char *driver_override, *old = mc_dev->driver_override;
+ char *cp;
+
+ if (WARN_ON(dev->bus != &fsl_mc_bus_type))
+ return -EINVAL;
+
+ if (count >= (PAGE_SIZE - 1))
+ return -EINVAL;
+
+ driver_override = kstrndup(buf, count, GFP_KERNEL);
+ if (!driver_override)
+ return -ENOMEM;
+
+ cp = strchr(driver_override, '\n');
+ if (cp)
+ *cp = '\0';
drop this strchr() ...

+ if (strlen(driver_override)) {
+ mc_dev->driver_override = driver_override;
+ } else {
+ kfree(driver_override);
+ mc_dev->driver_override = NULL;
+ }
+
+ kfree(old);
+
+ return count;
+}
+
+static ssize_t driver_override_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct fsl_mc_device *mc_dev = to_fsl_mc_device(dev);
+
+ return snprintf(buf, PAGE_SIZE, "%s\n", mc_dev->driver_override);
and also the terminating '\n' here.

+}
+static DEVICE_ATTR_RW(driver_override);
+
static struct attribute *fsl_mc_dev_attrs[] = {
&dev_attr_modalias.attr,
+ &dev_attr_driver_override.attr,
NULL,
};
@@ -704,6 +755,9 @@ EXPORT_SYMBOL_GPL(fsl_mc_device_add);
*/
void fsl_mc_device_remove(struct fsl_mc_device *mc_dev)
{
+ kfree(mc_dev->driver_override);
+ mc_dev->driver_override = NULL;
+
/*
* The device-specific remove callback will get invoked by device_del()
*/
diff --git a/include/linux/fsl/mc.h b/include/linux/fsl/mc.h
index 54d9436600c7..88095fd30c80 100644
--- a/include/linux/fsl/mc.h
+++ b/include/linux/fsl/mc.h
@@ -194,6 +194,7 @@ struct fsl_mc_device {
struct fsl_mc_device_irq **irqs;
struct fsl_mc_resource *resource;
struct device_link *consumer_link;
+ const char *driver_override;
We probably don't want const here.

OK


---
Best Regards, Laurentiu

};
#define to_fsl_mc_device(_dev) \


Diana