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Subject[PATCH 09/11] parport: Add comments for parport_register_dev_model()
Date
In preparation to remove parport_register_device(), copy the comments
to parport_register_dev_model() and modify the parameters according to
what parport_register_dev_model() has.

Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
drivers/parport/share.c | 62 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/parport.h | 4 ++++
2 files changed, 66 insertions(+)

diff --git a/drivers/parport/share.c b/drivers/parport/share.c
index 3169feebdc19..ee2892a935d6 100644
--- a/drivers/parport/share.c
+++ b/drivers/parport/share.c
@@ -841,6 +841,68 @@ static void free_pardevice(struct device *dev)
kfree(par_dev);
}

+/**
+ * parport_register_dev_model - register a device on a parallel port
+ * @port: port to which the device is attached
+ * @name: a name to refer to the device
+ * @par_dev_cb: struct containing callbacks
+ * @id: device number to be given to the device
+ *
+ * This function, called by parallel port device drivers,
+ * declares that a device is connected to a port, and tells the
+ * system all it needs to know.
+ *
+ * The struct pardev_cb contains pointer to callbacks. preemption
+ * callback function, @preempt, is called when this device driver
+ * has claimed access to the port but another device driver wants
+ * to use it. It is given, @private, as its parameter, and should
+ * return zero if it is willing for the system to release the port
+ * to another driver on its behalf. If it wants to keep control of
+ * the port it should return non-zero, and no action will be taken.
+ * It is good manners for the driver to try to release the port at
+ * the earliest opportunity after its preemption callback rejects a
+ * preemption attempt. Note that if a preemption callback is happy
+ * for preemption to go ahead, there is no need to release the
+ * port; it is done automatically. This function may not block, as
+ * it may be called from interrupt context. If the device driver
+ * does not support preemption, @preempt can be %NULL.
+ *
+ * The wake-up ("kick") callback function, @wakeup, is called when
+ * the port is available to be claimed for exclusive access; that
+ * is, parport_claim() is guaranteed to succeed when called from
+ * inside the wake-up callback function. If the driver wants to
+ * claim the port it should do so; otherwise, it need not take
+ * any action. This function may not block, as it may be called
+ * from interrupt context. If the device driver does not want to
+ * be explicitly invited to claim the port in this way, @wakeup can
+ * be %NULL.
+ *
+ * The interrupt handler, @irq_func, is called when an interrupt
+ * arrives from the parallel port. Note that if a device driver
+ * wants to use interrupts it should use parport_enable_irq(),
+ * and can also check the irq member of the parport structure
+ * representing the port.
+ *
+ * The parallel port (lowlevel) driver is the one that has called
+ * request_irq() and whose interrupt handler is called first.
+ * This handler does whatever needs to be done to the hardware to
+ * acknowledge the interrupt (for PC-style ports there is nothing
+ * special to be done). It then tells the IEEE 1284 code about
+ * the interrupt, which may involve reacting to an IEEE 1284
+ * event depending on the current IEEE 1284 phase. After this,
+ * it calls @irq_func. Needless to say, @irq_func will be called
+ * from interrupt context, and may not block.
+ *
+ * The %PARPORT_DEV_EXCL flag is for preventing port sharing, and
+ * so should only be used when sharing the port with other device
+ * drivers is impossible and would lead to incorrect behaviour.
+ * Use it sparingly! Normally, @flags will be zero.
+ *
+ * This function returns a pointer to a structure that represents
+ * the device on the port, or %NULL if there is not enough memory
+ * to allocate space for that structure.
+ **/
+
struct pardevice *
parport_register_dev_model(struct parport *port, const char *name,
const struct pardev_cb *par_dev_cb, int id)
diff --git a/include/linux/parport.h b/include/linux/parport.h
index 13932ce8b37b..36a0f6270238 100644
--- a/include/linux/parport.h
+++ b/include/linux/parport.h
@@ -337,6 +337,10 @@ struct pardevice *parport_register_device(struct parport *port,
void (*irq_func)(void *),
int flags, void *handle);

+/*
+ * parport_register_dev_model declares that a device is connected to a
+ * port, and tells the kernel all it needs to know.
+ */
struct pardevice *
parport_register_dev_model(struct parport *port, const char *name,
const struct pardev_cb *par_dev_cb, int cnt);
--
2.11.0
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