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The tape device type 3590/3592 and emulated 3490 VTS can handle a block size of up to 256K bytes. Currently the tape device driver is limited to a block size of 65535 bytes (64K-1). This limitation stems from the maximum of 65535 bytes of data that can be transferred with one Channel-Command Word (CCW). To work around this limitation data chaining is used which uses several CCW to transfer an entire 256K block of data. A single CCW holds a maximum of 65535 bytes of data. Set MAX_BLOCKSIZE to 262144 (= 256K) to allow for data transfers with larger block sizes. The read_block() and write_block() discipline functions calculate the number of CCWs required based on the IDAL buffer array size that was created for a given block size. If there is more than one CCW required for the data transfer, the new helper function tape_ccw_dc_idal() is used to build the data chain accordingly. The Interruption-Repsonse Block (irb) is added to the tape_request struct so that the tapechar_read/write() functions can analyze what data was read or written accordingly. Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com> Reviewed-by: Jens Remus <jremus@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.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 reStructuredText 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.