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Converted legacy readme from .md to .rst
Revert "Converted legacy readme from .md to .rst"
This reverts commit e33fef7a5aaa5dd377f87b90a667a2704b9fb834.
With TCD set to loop, there is a window where the
DMA has raised Done, but not reloaded the TCD, resetting
count and clearing Done.
In this window imxrt_dmach_getcount could then return 0.
Resulting in imxrt_dma_nextrx returning RXDMA_BUFFER_SIZE.
Which is not a valid index in the FIFO.
Since the count will be set to RXDMA_BUFFER_SIZE. When the DMA
engine completes the TCD reload. The imxrt_dma_nextrx would
return 0. Therefore:
(RXDMA_BUFFER_SIZE - dmaresidual) % RXDMA_BUFFER_SIZE
accomplishes this.
With TCD set to loop, there is a window where the
DMA has raised Done, but not reloaded the TCD, resetting
count and clearing Done.
In this window imxrt_dmach_getcount could then return 0.
Resulting in imxrt_dma_nextrx returning RXDMA_BUFFER_SIZE.
Which is not a valid index in the FIFO.
Since the count will be set to RXDMA_BUFFER_SIZE. When the DMA
engine completes the TCD reload. The imxrt_dma_nextrx would
return 0. Therefore:
(RXDMA_BUFFER_SIZE - dmaresidual) % RXDMA_BUFFER_SIZE
accomplishes this.
With TCD set to loop, there is a window where the
DMA has raised Done, but not reloaded the TCD, resetting
count and clearing Done.
In this window imxrt_dmach_getcount could then return 0.
Resulting in imxrt_dma_nextrx returning RXDMA_BUFFER_SIZE.
Which is not a valid index in the FIFO.
Since the count will be set to RXDMA_BUFFER_SIZE. When the DMA
engine completes the TCD reload. The imxrt_dma_nextrx would
return 0. Therefore:
(RXDMA_BUFFER_SIZE - dmaresidual) % RXDMA_BUFFER_SIZE
accomplishes this.
VELAPLATFO-18473
refs:
https://man7.org/linux/man-pages/man2/fcntl.2.html
If the FD_CLOEXEC bit is set, the file descriptor will automatically
be closed during a successful execve(2).
(If the execve(2) fails, the file descriptor is left open.)
modify:
1. Ensure that the child task copies all fds of the parent task,
including those with O_CLOEXE.
2. Make sure spawn_file_action is executed under fd with O_CLOEXEC,
otherwise it will fail.
3. When a new task is activated or exec is called, close all fds
with O_CLOEXEC flags.
Signed-off-by: dongjiuzhu1 <dongjiuzhu1@xiaomi.com>
refs: https://man7.org/linux/man-pages/man2/dup.2.html
The two file descriptors do not share file descriptor flags (the
close-on-exec flag). The close-on-exec flag (FD_CLOEXEC; see
fcntl(2)) for the duplicate descriptor is off.
Signed-off-by: dongjiuzhu1 <dongjiuzhu1@xiaomi.com>
