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Subject[PATCH 02/23] tty: add kernel-doc for tty_port
Date
tty_port used to have only short comments along its members. Convert
them into proper kernel-doc comments in front of the structure. And add
some more explanation to them where needed.

The whole structure purpose and handling is documented at the end too --
some pieces of preexisting text moved to this place.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
include/linux/tty_port.h | 104 ++++++++++++++++++++++++++-------------
1 file changed, 70 insertions(+), 34 deletions(-)

diff --git a/include/linux/tty_port.h b/include/linux/tty_port.h
index 6e86e9e118b6..9091e1c8de4c 100644
--- a/include/linux/tty_port.h
+++ b/include/linux/tty_port.h
@@ -7,17 +7,6 @@
#include <linux/tty_buffer.h>
#include <linux/wait.h>

-/*
- * Port level information. Each device keeps its own port level information
- * so provide a common structure for those ports wanting to use common support
- * routines.
- *
- * The tty port has a different lifetime to the tty so must be kept apart.
- * In addition be careful as tty -> port mappings are valid for the life
- * of the tty object but in many cases port -> tty mappings are valid only
- * until a hangup so don't use the wrong path.
- */
-
struct attribute_group;
struct tty_driver;
struct tty_port;
@@ -48,30 +37,77 @@ struct tty_port_client_operations {

extern const struct tty_port_client_operations tty_port_default_client_ops;

+/**
+ * struct tty_port -- port level information
+ *
+ * @buf: buffer for this port, locked internally
+ * @tty: back pointer to &struct tty_struct, valid only if the tty is open. Use
+ * tty_port_tty_get() to obtain it (and tty_kref_put() to release).
+ * @itty: internal back pointer to &struct tty_struct. Avoid this. It should be
+ * eliminated in the long term.
+ * @ops: tty port operations (like activate, shutdown), see &struct
+ * tty_port_operations
+ * @client_ops: tty port client operations (like receive_buf, write_wakeup).
+ * By default, tty_port_default_client_ops is used.
+ * @lock: lock protecting @tty
+ * @blocked_open: # of procs waiting for open in tty_port_block_til_ready()
+ * @count: usage count
+ * @open_wait: open waiters queue (waiting e.g. for a carrier)
+ * @delta_msr_wait: modem status change queue (waiting for MSR changes)
+ * @flags: user TTY flags (%ASYNC_)
+ * @iflags: internal flags (%TTY_PORT_)
+ * @console: when set, the port is a console
+ * @mutex: locking, for open, shutdown and other port operations
+ * @buf_mutex: @xmit_buf alloc lock
+ * @xmit_buf: optional xmit buffer used by some drivers
+ * @close_delay: delay in jiffies to wait when closing the port
+ * @closing_wait: delay in jiffies for output to be sent before closing
+ * @drain_delay: set to zero if no pure time based drain is needed else set to
+ * size of fifo
+ * @kref: references counter. Reaching zero calls @ops->destruct() if non-%NULL
+ * or frees the port otherwise.
+ * @client_data: pointer to private data, for @client_ops
+ *
+ * Each device keeps its own port level information. &struct tty_port was
+ * introduced as a common structure for such information. As every TTY device
+ * shall have a backing tty_port structure, every driver can use these members.
+ *
+ * The tty port has a different lifetime to the tty so must be kept apart.
+ * In addition be careful as tty -> port mappings are valid for the life
+ * of the tty object but in many cases port -> tty mappings are valid only
+ * until a hangup so don't use the wrong path.
+ *
+ * Tty port shall be initialized by tty_port_init() and shut down either by
+ * tty_port_destroy() (refcounting not used), or tty_port_put() (refcounting).
+ *
+ * There is a lot of helpers around &struct tty_port too. To name the most
+ * significant ones: tty_port_open(), tty_port_close() (or
+ * tty_port_close_start() and tty_port_close_end() separately if need be), and
+ * tty_port_hangup(). These call @ops->activate() and @ops->shutdown() as
+ * needed.
+ */
struct tty_port {
- struct tty_bufhead buf; /* Locked internally */
- struct tty_struct *tty; /* Back pointer */
- struct tty_struct *itty; /* internal back ptr */
- const struct tty_port_operations *ops; /* Port operations */
- const struct tty_port_client_operations *client_ops; /* Port client operations */
- spinlock_t lock; /* Lock protecting tty field */
- int blocked_open; /* Waiting to open */
- int count; /* Usage count */
- wait_queue_head_t open_wait; /* Open waiters */
- wait_queue_head_t delta_msr_wait; /* Modem status change */
- unsigned long flags; /* User TTY flags ASYNC_ */
- unsigned long iflags; /* Internal flags TTY_PORT_ */
- unsigned char console:1; /* port is a console */
- struct mutex mutex; /* Locking */
- struct mutex buf_mutex; /* Buffer alloc lock */
- unsigned char *xmit_buf; /* Optional buffer */
- unsigned int close_delay; /* Close port delay */
- unsigned int closing_wait; /* Delay for output */
- int drain_delay; /* Set to zero if no pure time
- based drain is needed else
- set to size of fifo */
- struct kref kref; /* Ref counter */
- void *client_data;
+ struct tty_bufhead buf;
+ struct tty_struct *tty;
+ struct tty_struct *itty;
+ const struct tty_port_operations *ops;
+ const struct tty_port_client_operations *client_ops;
+ spinlock_t lock;
+ int blocked_open;
+ int count;
+ wait_queue_head_t open_wait;
+ wait_queue_head_t delta_msr_wait;
+ unsigned long flags;
+ unsigned long iflags;
+ unsigned char console:1;
+ struct mutex mutex;
+ struct mutex buf_mutex;
+ unsigned char *xmit_buf;
+ unsigned int close_delay;
+ unsigned int closing_wait;
+ int drain_delay;
+ struct kref kref;
+ void *client_data;
};

/* tty_port::iflags bits -- use atomic bit ops */
--
2.34.0
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