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Application A has registered a diag buffer and looking for particular event to happen to release & read the trace buffer. Meanwhile application B has unregistered the diag buffer and now Application A can't get the required diag buffer. So proper diag buffer ownership is missing. Each application has to maintain its own Unique ID. Now driver has to save the Application's UniqueID for each diag buffer type when diag buffer is registered. And driver has to allow 'release', 'read' & 'unregister' diag commands only if application's UniqueID matches with saved UniqueID for the corresponding diag buffer type. When diag buffer is registered by the driver, then the UniqueID saved by the driver is "BRCM" (i.e. 0x4252434D) for SAS3 and above generations HBA devices. For SAS2 HBAs, driver keeps the legacy UniqueID 0x07075900 for maintaining compatibility with the legacy SAS2 application and this improvement won't be applicable for SAS2 HBA devices. Any application can own the buffer registered by the driver by sending diag register request to driver with same buffer type and size (Application can get the buffer size by sending 'query' command). Then driver changes the ownership of the buffer by saving application's UniqueID for that corresponding buffer type. Also, application can re-register the diag buffer with same size without un-registering it, but diag buffer should be released before re-registering it. By allowing this, driver no need to deallocate and allocate a new buffer for re-register command, same buffer can be re-used. Link: https://lore.kernel.org/r/1568379890-18347-6-git-send-email-sreekanth.reddy@broadcom.com Signed-off-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.