diff options
| -rw-r--r-- | include/linux/console.h | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/include/linux/console.h b/include/linux/console.h index 35c64ee3827b..46b3c210b931 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -372,6 +372,49 @@ struct console { */ void (*write_atomic)(struct console *con, struct nbcon_write_context *wctxt); + /** + * @device_lock: + * + * NBCON callback to begin synchronization with driver code. + * + * Console drivers typically must deal with access to the hardware + * via user input/output (such as an interactive login shell) and + * output of kernel messages via printk() calls. This callback is + * called by the printk-subsystem whenever it needs to synchronize + * with hardware access by the driver. It should be implemented to + * use whatever synchronization mechanism the driver is using for + * itself (for example, the port lock for uart serial consoles). + * + * The callback is always called from task context. It may use any + * synchronization method required by the driver. + * + * IMPORTANT: The callback MUST disable migration. The console driver + * may be using a synchronization mechanism that already takes + * care of this (such as spinlocks). Otherwise this function must + * explicitly call migrate_disable(). + * + * The flags argument is provided as a convenience to the driver. It + * will be passed again to device_unlock(). It can be ignored if the + * driver does not need it. + */ + void (*device_lock)(struct console *con, unsigned long *flags); + + /** + * @device_unlock: + * + * NBCON callback to finish synchronization with driver code. + * + * It is the counterpart to device_lock(). + * + * This callback is always called from task context. It must + * appropriately re-enable migration (depending on how device_lock() + * disabled migration). + * + * The flags argument is the value of the same variable that was + * passed to device_lock(). + */ + void (*device_unlock)(struct console *con, unsigned long flags); + atomic_t __private nbcon_state; atomic_long_t __private nbcon_seq; struct printk_buffers *pbufs; |