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SubjectRe: [PATCH 03/10] bus/fsl-mc: add support for 'driver_override' in the mc-bus
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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@nxp.com>
>>
>> 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@nxp.com>
>> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
>> Signed-off-by: Diana Craciun <diana.craciun@oss.nxp.com>
>> ---
>> 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@freescale.com>
>> *
>> */
>> @@ -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

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