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The SDHCI spec also offers an "advanced DMA" mode where we can use scatter-gather lists. It would allow to remove several of the DMA restrictions, but hardware support for it is optional, so we need this version anyway. The geometry is retrieved on demand in the first read or write or in a call to the get geometry or get device size ioctl. It is not possible to retrieve it from the device initialization because that is called as part of the mmc_bus scanning, which needs a specific sequence of commands and keeps the bus locked to prevent drivers to insert their own commands in the middle of that sequence. TODO: - Move the DMA restrictions definition to sdhci_pci and forward it up to mmc_disk (which is the one creating the IOScheduler) - Decide if we want to keep non-DMA support (probably should, but it makes things more complex, because it uses virtual addresses) Change-Id: Ib1dd14eacf62052d747bfb3ef7820bc5a34d3030 Reviewed-on: https://review.haiku-os.org/c/haiku/+/3471 Reviewed-by: Alex von Gluck IV <kallisti5@unixzen.com>