Re: [PATCH v4 2/2] firmware: google: Expose coreboot tables over sysfs

From: Stephen Boyd
Date: Thu Jun 25 2020 - 03:10:55 EST


Quoting patrick.rudolph@xxxxxxxxxxxxx (2020-04-07 01:29:07)
> From: Patrick Rudolph <patrick.rudolph@xxxxxxxxxxxxx>
>
> Make all coreboot table entries available to userland. This is useful for
> tools that are currently using /dev/mem.
>
> Besides the tag and size also expose the raw table data itself.
>
> Update the ABI documentation to explain the new sysfs interface.
>
> Tools can easily scan for the right coreboot table by reading
> /sys/bus/coreboot/devices/coreboot*/attributes/id
> The binary table data can then be read from
> /sys/bus/coreboot/devices/coreboot*/attributes/data
>
> Signed-off-by: Patrick Rudolph <patrick.rudolph@xxxxxxxxxxxxx>
> ---

Reviewed-by: Stephen Boyd <swboyd@xxxxxxxxxxxx>

Minor nits below:

> -v2:
> - Add ABI documentation
> - Add 0x prefix on hex values
> - Remove wrong ioremap hint as found by CI
> -v3:
> - Use BIN_ATTR_RO
> -v4:
> - Updated ABI documentation
> ---
> Documentation/ABI/stable/sysfs-bus-coreboot | 30 +++++++++++
> drivers/firmware/google/coreboot_table.c | 58 +++++++++++++++++++++
> 2 files changed, 88 insertions(+)
>
> diff --git a/Documentation/ABI/stable/sysfs-bus-coreboot b/Documentation/ABI/stable/sysfs-bus-coreboot
> index 6055906f41f2..328153a1b3f4 100644
> --- a/Documentation/ABI/stable/sysfs-bus-coreboot
> +++ b/Documentation/ABI/stable/sysfs-bus-coreboot
> diff --git a/drivers/firmware/google/coreboot_table.c b/drivers/firmware/google/coreboot_table.c
> index 0205987a4fd4..d0fc3eb93f4f 100644
> --- a/drivers/firmware/google/coreboot_table.c
> +++ b/drivers/firmware/google/coreboot_table.c
> @@ -3,9 +3,11 @@
> * coreboot_table.c
> *
> * Module providing coreboot table access.
> + * Exports coreboot tables as attributes in sysfs.
> *
> * Copyright 2017 Google Inc.
> * Copyright 2017 Samuel Holland <samuel@xxxxxxxxxxxx>
> + * Copyright 2019 9elements Agency GmbH
> */
>
> #include <linux/acpi.h>
> @@ -84,6 +86,60 @@ void coreboot_driver_unregister(struct coreboot_driver *driver)
> }
> EXPORT_SYMBOL(coreboot_driver_unregister);
>
> +static ssize_t id_show(struct device *dev,
> + struct device_attribute *attr, char *buffer)
> +{
> + struct coreboot_device *device = CB_DEV(dev);

Wouldn't hurt to throw const in front of these.

> +
> + return sprintf(buffer, "0x%08x\n", device->entry.tag);
> +}
> +
> +static ssize_t size_show(struct device *dev,
> + struct device_attribute *attr, char *buffer)
> +{
> + struct coreboot_device *device = CB_DEV(dev);

And these. But the function is so short probably doesn't really matter.

> +
> + return sprintf(buffer, "%u\n", device->entry.size);
> +}
> +
> +static DEVICE_ATTR_RO(id);
> +static DEVICE_ATTR_RO(size);
> +
> +static struct attribute *cb_dev_attrs[] = {
> + &dev_attr_id.attr,
> + &dev_attr_size.attr,
> + NULL
> +};
> +
> +static ssize_t data_read(struct file *filp, struct kobject *kobj,
> + struct bin_attribute *bin_attr,
> + char *buffer, loff_t offset, size_t count)
> +{
> + struct device *dev = kobj_to_dev(kobj);
> + struct coreboot_device *device = CB_DEV(dev);
> +
> + return memory_read_from_buffer(buffer, count, &offset,
> + &device->entry, device->entry.size);
> +}
> +
> +static BIN_ATTR_RO(data, 0);

Still no way to figure out the actual size? Can we add the bin_attribute
at runtime?

> +
> +static struct bin_attribute *cb_dev_bin_attrs[] = {
> + &bin_attr_data,
> + NULL
> +};
> +