From dd05add7b2b6004c5fa3a1f276f56d8668f86b65 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Sat, 26 Sep 2026 19:20:30 -0300 Subject: netfs: zero the tail of a short DIO/unbuffered read The buffered read collector zero-fills the tail of a short read that stops below the inode's i_size (netfs_clear_unread()), so a read that races an extending write still returns the expected number of bytes. The non-buffered collector path does no such thing: it just records how much was transferred. Add the same zero-fill for the non-buffered case, gated on NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short result from it is known to be safe to treat as a hole, as opposed to NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of the file and should be reported short as-is. Only CLEAR_TAIL should zero-fill here; a real EOF must stay a real short read. No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest, so this is inert on its own -- a following change teaches cifs to set it in the one case that needs it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reviewed-by: David Howells Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org --- Documentation/driver-api/fpga/fpga-programming.rst | 107 +++++++++++++++++++++ 1 file changed, 107 insertions(+) create mode 100644 Documentation/driver-api/fpga/fpga-programming.rst (limited to 'Documentation/driver-api/fpga/fpga-programming.rst') diff --git a/Documentation/driver-api/fpga/fpga-programming.rst b/Documentation/driver-api/fpga/fpga-programming.rst new file mode 100644 index 000000000..fb4da4240 --- /dev/null +++ b/Documentation/driver-api/fpga/fpga-programming.rst @@ -0,0 +1,107 @@ +In-kernel API for FPGA Programming +================================== + +Overview +-------- + +The in-kernel API for FPGA programming is a combination of APIs from +FPGA manager, bridge, and regions. The actual function used to +trigger FPGA programming is fpga_region_program_fpga(). + +fpga_region_program_fpga() uses functionality supplied by +the FPGA manager and bridges. It will: + + * lock the region's mutex + * lock the mutex of the region's FPGA manager + * build a list of FPGA bridges if a method has been specified to do so + * disable the bridges + * program the FPGA using info passed in :c:expr:`fpga_region->info`. + * re-enable the bridges + * release the locks + +The struct fpga_image_info specifies what FPGA image to program. It is +allocated/freed by fpga_image_info_alloc() and freed with +fpga_image_info_free() + +How to program an FPGA using a region +------------------------------------- + +When the FPGA region driver probed, it was given a pointer to an FPGA manager +driver so it knows which manager to use. The region also either has a list of +bridges to control during programming or it has a pointer to a function that +will generate that list. Here's some sample code of what to do next:: + + #include + #include + + struct fpga_image_info *info; + int ret; + + /* + * First, alloc the struct with information about the FPGA image to + * program. + */ + info = fpga_image_info_alloc(dev); + if (!info) + return -ENOMEM; + + /* Set flags as needed, such as: */ + info->flags = FPGA_MGR_PARTIAL_RECONFIG; + + /* + * Indicate where the FPGA image is. This is pseudo-code; you're + * going to use one of these three. + */ + if (image is in a scatter gather table) { + + info->sgt = [your scatter gather table] + + } else if (image is in a buffer) { + + info->buf = [your image buffer] + info->count = [image buffer size] + + } else if (image is in a firmware file) { + + info->firmware_name = devm_kstrdup(dev, firmware_name, + GFP_KERNEL); + + } + + /* Add info to region and do the programming */ + region->info = info; + ret = fpga_region_program_fpga(region); + + /* Deallocate the image info if you're done with it */ + region->info = NULL; + fpga_image_info_free(info); + + if (ret) + return ret; + + /* Now enumerate whatever hardware has appeared in the FPGA. */ + +API for programming an FPGA +--------------------------- + +* fpga_region_program_fpga() - Program an FPGA +* fpga_image_info() - Specifies what FPGA image to program +* fpga_image_info_alloc() - Allocate an FPGA image info struct +* fpga_image_info_free() - Free an FPGA image info struct + +.. kernel-doc:: drivers/fpga/fpga-region.c + :functions: fpga_region_program_fpga + +FPGA Manager flags + +.. kernel-doc:: include/linux/fpga/fpga-mgr.h + :doc: FPGA Manager flags + +.. kernel-doc:: include/linux/fpga/fpga-mgr.h + :functions: fpga_image_info + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_image_info_alloc + +.. kernel-doc:: drivers/fpga/fpga-mgr.c + :functions: fpga_image_info_free -- cgit v1.3.1