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fpga: Clarify how write_init works streaming modes

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This interface was designed for streaming, but write_init's buf
argument has an unclear purpose. Define it to be the first bytes
of the bitstream. Each driver gets to set how many bytes (at most)
it wants to see. Short bitstreams will be passed through as-is, while
long ones will be truncated.

The intent is to allow drivers to peek at the header before the transfer
actually starts.

Signed-off-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Acked-by: Alan Tull <atull@opensource.altera.com>
This commit is contained in:
Jason Gunthorpe 2016-11-22 18:22:09 +00:00 • committed by Alan Tull
parent 340c0c53ea
commit 1d7f1589d3
4 changed files with 11 additions and 3 deletions
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6
drivers/fpga/fpga-mgr.c
View file

@ -53,10 +53,12 @@ int fpga_mgr_buf_load(struct fpga_manager *mgr, struct fpga_image_info *info,
/*
* Call the low level driver's write_init function. This will do the
* device-specific things to get the FPGA into the state where it is
* ready to receive an FPGA image.
* ready to receive an FPGA image. The low level driver only gets to
* see the first initial_header_size bytes in the buffer.
*/
mgr->state = FPGA_MGR_STATE_WRITE_INIT;
ret = mgr->mops->write_init(mgr, info, buf, count);
ret = mgr->mops->write_init(mgr, info, buf,
min(mgr->mops->initial_header_size, count));
if (ret) {
dev_err(dev, "Error preparing FPGA for writing\n");
mgr->state = FPGA_MGR_STATE_WRITE_INIT_ERR;