Re: [PATCH v10 6/7] i3c: master: sysfs key for acquire bus

Alexandre Belloni
2021-06-08T23:33:36Z

On 30/11/2020 07:20:02+0100, Parshuram Thombare wrote:
> Added support to acquire I3C bus through sysfs interface.
>
> Signed-off-by: Parshuram Thombare <pthombar@cadence.com>
> ---
> drivers/i3c/master.c | 18 ++++++++++++++++++
> 1 files changed, 18 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
> index c01ba00..beb7495 100644
> --- a/drivers/i3c/master.c
> +++ b/drivers/i3c/master.c
> @@ -581,6 +581,23 @@ static ssize_t i2c_scl_frequency_show(struct device *dev,
> }
> static DEVICE_ATTR_RO(i2c_scl_frequency);
>
> +static ssize_t i3c_acquire_bus_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct i3c_master_controller *master = dev_to_i3cmaster(dev);
> + int ret;
> +
> + i3c_bus_normaluse_lock(&master->bus);
> + ret = i3c_master_acquire_bus(master);
> + i3c_bus_normaluse_unlock(&master->bus);
> + if (!ret)
> + i3c_master_enable_mr_events(master);
> +
> + return ret ?: count;
> +}
> +static DEVICE_ATTR_WO(i3c_acquire_bus);
> +

I'm wondering whether we should allow userspace to actually control
that. Shouldn't we simply request mastership when a driver needs to talk
to a device on the bus? Is it really useful to have that until there is
an i3c-dev userspace interface?

> static struct attribute *i3c_masterdev_attrs[] = {
> &dev_attr_mode.attr,
> &dev_attr_current_master.attr,
> @@ -591,6 +608,7 @@ static ssize_t i2c_scl_frequency_show(struct device *dev,
> &dev_attr_pid.attr,
> &dev_attr_dynamic_address.attr,
> &dev_attr_hdrcap.attr,
> + &dev_attr_i3c_acquire_bus.attr,
> NULL,
> };
> ATTRIBUTE_GROUPS(i3c_masterdev);
> --
> 1.7.1
>

--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering