This is a small helper function which sends the SR_DF_HEADER packet that
drivers usually emit in their hw_dev_acquisition_start() API callback.
It simplifies and shortens the hw_dev_acquisition_start() functions
quite a bit.
It also simplifies the input modules which send an SR_DF_HEADER packet, too.
This patch also automatically removes some unneeded malloc/free in some
drivers for the 'packet' and 'header' structs used for SR_DF_HEADER.
Check the relevant arguments for != NULL before calling the actual
driver-specific function, so that the driver can safely assume those
arguments are non-NULL. This removes the need to duplicate these
checks in every driver.
Also, do some minor whitespace and consistency improvements.
Sending an SR_DF_META packet at the start of every stream is not
mandatory; the frontend should ask for what it needs, and any extra
information the driver wants to send will come in due time.
In the case of USB drivers, a driver's dev_acquisition_stop() cannot
simply remove its fd sources from the session and close its devices:
a USB transfer might still be underway, and it needs to be finished
(and its memory freed) properly.
An sr_dev_inst->status value is added: SR_ST_STOPPING, which should
be set when the driver's dev_acquisition_stop() is called, and acts
as a marker for the USB event handler to wind up its operations.
In order for dev_acquisition_stop() to be able to set the sdi status,
however, it needs to be unconstified.
These are used to list the device instances currently known to the driver,
and clear that list.
Drivers that don't necessarily clear their list of instances on every scan,
such as genericdmm, need to provide these to the frontend to keep instance
management sane.
Since probes now live in a struct sr_dev_inst owned by the driver, it
already knows about them. Instead of a frontend telling the driver to
configure probes, all driver now do this just before starting acquisition.
It's obsolete: no frontend ever used it, and neither did libsigrok.
The sdi->status field is only used internally by some drivers, and
should probably be moved to the driver-specific context structs.
Uwe Hermann
Bert Vermeulen
Peter Stuge