[PATCH v2 09/15] peci: Add sysfs interface for PECI bus

[Winiarska, Iwona <iwona.winiarska@intel.com>]

On Fri, 2021-08-27 at 12:11 -0700, Dan Williams wrote:
> On Tue, Aug 3, 2021 at 4:35 AM Iwona Winiarska
> <iwona.winiarska@intel.com> wrote:
> > 
> > PECI devices may not be discoverable at the time when PECI controller is
> > being added (e.g. BMC can boot up when the Host system is still in S5).
> > Since we currently don't have the capabilities to figure out the Host
> > system state inside the PECI subsystem itself, we have to rely on
> > userspace to do it for us.
> > 
> > In the future, PECI subsystem may be expanded with mechanisms that allow
> > us to avoid depending on userspace interaction (e.g. CPU presence could
> > be detected using GPIO, and the information on whether it's discoverable
> > could be obtained over IPMI).
> 
> Thanks for this detail.
> 
> > Unfortunately, those methods may ultimately not be available (support
> > will vary from platform to platform), which means that we still need
> > platform independent method triggered by userspace.
> > 
> > Signed-off-by: Iwona Winiarska <iwona.winiarska@intel.com>
> > ---
> > ?Documentation/ABI/testing/sysfs-bus-peci | 16 +++++
> > ?drivers/peci/Makefile??????????????????? |? 2 +-
> > ?drivers/peci/core.c????????????????????? |? 3 +-
> > ?drivers/peci/device.c??????????????????? |? 1 +
> > ?drivers/peci/internal.h????????????????? |? 5 ++
> > ?drivers/peci/sysfs.c???????????????????? | 82 ++++++++++++++++++++++++
> > ?6 files changed, 107 insertions(+), 2 deletions(-)
> > ?create mode 100644 Documentation/ABI/testing/sysfs-bus-peci
> > ?create mode 100644 drivers/peci/sysfs.c
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-bus-peci
> > b/Documentation/ABI/testing/sysfs-bus-peci
> > new file mode 100644
> > index 000000000000..56c2b2216bbd
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-bus-peci
> > @@ -0,0 +1,16 @@
> > +What:????????? /sys/bus/peci/rescan
> > +Date:????????? July 2021
> > +KernelVersion: 5.15
> > +Contact:?????? Iwona Winiarska <iwona.winiarska@intel.com>
> > +Description:
> > +?????????????? Writing a non-zero value to this attribute will
> > +?????????????? initiate scan for PECI devices on all PECI controllers
> > +?????????????? in the system.
> > +
> > +What:????????? /sys/bus/peci/devices/<controller_id>-<device_addr>/remove
> > +Date:????????? July 2021
> > +KernelVersion: 5.15
> > +Contact:?????? Iwona Winiarska <iwona.winiarska@intel.com>
> > +Description:
> > +?????????????? Writing a non-zero value to this attribute will
> > +?????????????? remove the PECI device and any of its children.
> > diff --git a/drivers/peci/Makefile b/drivers/peci/Makefile
> > index c5f9d3fe21bb..917f689e147a 100644
> > --- a/drivers/peci/Makefile
> > +++ b/drivers/peci/Makefile
> > @@ -1,7 +1,7 @@
> > ?# SPDX-License-Identifier: GPL-2.0-only
> > 
> > ?# Core functionality
> > -peci-y := core.o request.o device.o
> > +peci-y := core.o request.o device.o sysfs.o
> > ?obj-$(CONFIG_PECI) += peci.o
> > 
> > ?# Hardware specific bus drivers
> > diff --git a/drivers/peci/core.c b/drivers/peci/core.c
> > index d143f1a7fe98..c473acb3c2a0 100644
> > --- a/drivers/peci/core.c
> > +++ b/drivers/peci/core.c
> > @@ -34,7 +34,7 @@ struct device_type peci_controller_type = {
> > ??????? .release??????? = peci_controller_dev_release,
> > ?};
> > 
> > -static int peci_controller_scan_devices(struct peci_controller *controller)
> > +int peci_controller_scan_devices(struct peci_controller *controller)
> > ?{
> > ??????? int ret;
> > ??????? u8 addr;
> > @@ -159,6 +159,7 @@ EXPORT_SYMBOL_NS_GPL(devm_peci_controller_add, PECI);
> > 
> > ?struct bus_type peci_bus_type = {
> > ??????? .name?????????? = "peci",
> > +?????? .bus_groups???? = peci_bus_groups,
> > ?};
> > 
> > ?static int __init peci_init(void)
> > diff --git a/drivers/peci/device.c b/drivers/peci/device.c
> > index 32811248997b..d77d9dabd51e 100644
> > --- a/drivers/peci/device.c
> > +++ b/drivers/peci/device.c
> > @@ -110,5 +110,6 @@ static void peci_device_release(struct device *dev)
> > ?}
> > 
> > ?struct device_type peci_device_type = {
> > +?????? .groups???????? = peci_device_groups,
> > ??????? .release??????? = peci_device_release,
> > ?};
> > diff --git a/drivers/peci/internal.h b/drivers/peci/internal.h
> > index 57d11a902c5d..978e12c8e1d3 100644
> > --- a/drivers/peci/internal.h
> > +++ b/drivers/peci/internal.h
> > @@ -8,6 +8,7 @@
> > ?#include <linux/types.h>
> > 
> > ?struct peci_controller;
> > +struct attribute_group;
> > ?struct peci_device;
> > ?struct peci_request;
> > 
> > @@ -19,12 +20,16 @@ struct peci_request *peci_request_alloc(struct
> > peci_device *device, u8 tx_len, u
> > ?void peci_request_free(struct peci_request *req);
> > 
> > ?extern struct device_type peci_device_type;
> > +extern const struct attribute_group *peci_device_groups[];
> > 
> > ?int peci_device_create(struct peci_controller *controller, u8 addr);
> > ?void peci_device_destroy(struct peci_device *device);
> > 
> > ?extern struct bus_type peci_bus_type;
> > +extern const struct attribute_group *peci_bus_groups[];
> 
> To me, sysfs.c is small enough to just fold into core.c, then no need
> to declare public attribute arrays like this, but up to you if you
> prefer the sysfs.c split.

Left the sysfs split for now.

> 
> > 
> > ?extern struct device_type peci_controller_type;
> > 
> > +int peci_controller_scan_devices(struct peci_controller *controller);
> > +
> > ?#endif /* __PECI_INTERNAL_H */
> > diff --git a/drivers/peci/sysfs.c b/drivers/peci/sysfs.c
> > new file mode 100644
> > index 000000000000..db9ef05776e3
> > --- /dev/null
> > +++ b/drivers/peci/sysfs.c
> > @@ -0,0 +1,82 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +// Copyright (c) 2021 Intel Corporation
> > +
> > +#include <linux/device.h>
> > +#include <linux/kernel.h>
> > +#include <linux/peci.h>
> > +
> > +#include "internal.h"
> > +
> > +static int rescan_controller(struct device *dev, void *data)
> > +{
> > +?????? if (dev->type != &peci_controller_type)
> > +?????????????? return 0;
> > +
> > +?????? return peci_controller_scan_devices(to_peci_controller(dev));
> > +}
> > +
> > +static ssize_t rescan_store(struct bus_type *bus, const char *buf, size_t
> > count)
> > +{
> > +?????? bool res;
> > +?????? int ret;
> > +
> > +?????? ret = kstrtobool(buf, &res);
> > +?????? if (ret)
> > +?????????????? return ret;
> > +
> > +?????? if (!res)
> > +?????????????? return count;
> > +
> > +?????? ret = bus_for_each_dev(&peci_bus_type, NULL, NULL,
> > rescan_controller);
> > +?????? if (ret)
> > +?????????????? return ret;
> > +
> > +?????? return count;
> > +}
> > +static BUS_ATTR_WO(rescan);
> > +
> > +static struct attribute *peci_bus_attrs[] = {
> > +?????? &bus_attr_rescan.attr,
> > +?????? NULL
> > +};
> > +
> > +static const struct attribute_group peci_bus_group = {
> > +?????? .attrs = peci_bus_attrs,
> > +};
> > +
> > +const struct attribute_group *peci_bus_groups[] = {
> > +?????? &peci_bus_group,
> > +?????? NULL
> > +};
> > +
> > +static ssize_t remove_store(struct device *dev, struct device_attribute
> > *attr,
> > +?????????????????????????? const char *buf, size_t count)
> > +{
> > +?????? struct peci_device *device = to_peci_device(dev);
> > +?????? bool res;
> > +?????? int ret;
> > +
> > +?????? ret = kstrtobool(buf, &res);
> > +?????? if (ret)
> > +?????????????? return ret;
> > +
> > +?????? if (res && device_remove_file_self(dev, attr))
> > +?????????????? peci_device_destroy(device);
> 
> How do you solve races between sysfs device remove and controller
> device remove? Looks like double-free at first glance. Have a look at
> the? kill_device() helper as one way to resolve this double-delete
> race..

Done.

Thanks
-Iwona

> 
> > +
> > +?????? return count;
> > +}
> > +static DEVICE_ATTR_IGNORE_LOCKDEP(remove, 0200, NULL, remove_store);
> > +
> > +static struct attribute *peci_device_attrs[] = {
> > +?????? &dev_attr_remove.attr,
> > +?????? NULL
> > +};
> > +
> > +static const struct attribute_group peci_device_group = {
> > +?????? .attrs = peci_device_attrs,
> > +};
> > +
> > +const struct attribute_group *peci_device_groups[] = {
> > +?????? &peci_device_group,
> > +?????? NULL
> > +};
> > --
> > 2.31.1
> >