On 2018-12-10 22:02, Wolfram Sang wrote:
> Some drivers open code handling of suspended adapters. It should be
> handled by the core, though, to ensure generic handling. This patch adds
> the flag and an accessor function.
>
> Signed-off-by: Wolfram Sang <wsa+rene...@sang-engineering.com>
> ---
> drivers/i2c/i2c-core-base.c | 1 +
> include/linux/i2c.h | 9 +++++++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 28460f6a60cc..9f89e258c8ff 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -1232,6 +1232,7 @@ static int i2c_register_adapter(struct i2c_adapter
> *adap)
> if (!adap->lock_ops)
> adap->lock_ops = &i2c_adapter_lock_ops;
>
> + adap->is_suspended = false;
> rt_mutex_init(&adap->bus_lock);
> rt_mutex_init(&adap->mux_lock);
> mutex_init(&adap->userspace_clients_lock);
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 65b4eaed1d96..9852038ee3a7 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -680,6 +680,7 @@ struct i2c_adapter {
> int timeout; /* in jiffies */
> int retries;
> struct device dev; /* the adapter device */
> + unsigned int is_suspended:1; /* owned by the I2C core */
When more stuff is added to this bit field (which always happens at
some point) updates to all members of the bit field will have to use
the same root-adapter-locking, or we will suffer from RMW-races. So
this feels like an invitation for future disaster. Maybe a comment
about that to remind our future selves? Or perhaps the bit field
should be avoided altogether?
Cheers,
Peter
>
> int nr;
> char name[48];
> @@ -762,6 +763,14 @@ i2c_unlock_bus(struct i2c_adapter *adapter, unsigned int
> flags)
> adapter->lock_ops->unlock_bus(adapter, flags);
> }
>
> +static inline void i2c_mark_adapter_suspended(struct i2c_adapter *adap,
> + bool suspended)
> +{
> + i2c_lock_bus(adap, I2C_LOCK_ROOT_ADAPTER);
> + adap->is_suspended = suspended;
> + i2c_unlock_bus(adap, I2C_LOCK_ROOT_ADAPTER);
> +}
> +
> /*flags for the client struct: */
> #define I2C_CLIENT_PEC 0x04 /* Use Packet Error Checking */
> #define I2C_CLIENT_TEN 0x10 /* we have a ten bit chip
> address */
>
