74b6097078
First implementation of reading sectors from an SD card. This is not the best performance for many reasons: - No DMA - Reads only one sector at a time - Cannot read more than 512 bytes per syscall Also there are major limitations: - Cannot read less than 512 bytes. The hardware of course works in full sectors. The mmc_disk driver should go through the io scheduler to make sure requests have a reasonable size and offset, and nothing tries to read just a few bytes in the middle of a sector. - SD cards only (no SDHC, no MMC) Architecture problems: I think too much of the implementation is done in sdhci_pci and should be moved to the upper layers. However it is difficult to say without having implemented DMA (which indeed will be at the low level of the sdhci controller). It doesn't help that the order of operations is a bit different depending on wether there is DMA or not. In DMA mode you first prepare the buffer, then run the command. In non-DMA mode you first send the command, then read the data into the buffer. We need an API at the mmc_bus level that doesn't care about that low-level detail. There are other things that the MMC bus should be doing however, such as switching to different clock speeds depending on which card is activated and how fast it can go. At least the following should be done: - The read method for mmc_bus and sdhci_pci should use a scatter-gather structure as a parameter instead of a single buffer - See if can be integrated into ExecuteCommand at sdhci level (it's essentially a command with an additional data phase) Change-Id: I688b6c694561074535c9c0c2545f06dc04b06e7d Reviewed-on: https://review.haiku-os.org/c/haiku/+/3466 Reviewed-by: Jérôme Duval <jerome.duval@gmail.com> |
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Haiku
Homepage | Mailing Lists | IRC Channels | Issue Tracker | API docs
Haiku is an open-source operating system that specifically targets personal computing. Inspired by the BeOS, Haiku is fast, simple to use, easy to learn and yet very powerful.
Goals
- Sensible defaults with minimal configuration required.
- Clean, clear, concise code.
- Unified desktop environment.
Trying Haiku
Haiku provides pre-built nightly images and release images. Haiku is compatible with a large variety of hardware, but in case you don't want to "take the plunge" and install Haiku on bare metal, you can install it on a virtual machine (VM) instead. If you've never used a VM before, you can follow one of the "Emulating Haiku" guides.
Compiling Haiku
See ReadMe.Compiling.
Contributing
Haiku is a meritocratic open source project with a large variety of tasks. Even if you can't write code, you can still help! Haiku needs designers, (technical) writers, translators, testers... Get involved and help out!
Contributing code
If you're submitting a patch to us, please make sure you're following the patch submitting guidelines.
If you're having trouble finding something in the source tree, you can use one of our web-based source code browsers:
- https://xref.landonf.org/ (OpenGrok, provided by Landon Fuller)
- https://git.haiku-os.org/ (git, provided by Haiku, Inc.)
Contributing documentation
The main piece of documentation that still needs work are the API docs (found
in the tree at docs/user). Just find an undocumented class, write
documentation for it, and submit a patch.
Contributing translations
See wiki:i18n.
Contributing software ports
See HaikuPorts.
Contributing to our infrastructure
See Infrastructure.