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| == Ideas for generic handling of devices == | | == Sections deserving their own page == |
| | * [[User_talk:MrNuke/Block_Device_API | IDEAPAGE: Generic handling of storage devices]] |
| | * [[User_talk:MrNuke/CBFS_Ideas | IDEAPAGE: CBFS partitioning support]] |
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| IMPORTANT! Feel free to edit this page to share your thoughts and ideas. This is the official MMC open brainstorming page.
| | == Testing ARM coreboot under qemu-system-arm == |
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| === Proposal 1: Unified API === | | Launch qemu with '''-serial stdio''' and pass kernel the '''console=tty''' option. (UNTESTED). |
| Chan is an IO channel.
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| This struct is used in Inferno and has been for a long time; so it works.
| | Run qemu-arm: |
| It's also in the opcodes somewhat like what we did for EMMC on ARM.
| | '''$ qemu-system-arm -M vexpress-a9 -m 1024M -serial stdio -kernel build/coreboot.rom''' |
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| struct Dev
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| {
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| char* name;
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| void (*reset)(void);
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| void (*init)(void);
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| void (*shutdown)(void);
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| Chan* (*attach)(char*); /* tell the device you want to use it */
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| Walkqid* (*walk)(Chan*, Chan*, char**, int); /* walk to a name in the device's managed name space; return a handle */
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| int (*stat)(Chan*, uchar*, int); // status info
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| Chan* (*open)(Chan*, int); /* get access to a resource in the device name space */
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| void (*close)(Chan*); /* tell it you are done with whatever it is. */
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| long (*read)(Chan*, void*, long, vlong);
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| long (*write)(Chan*, void*, long, vlong);
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| void (*power)(int); /* power mgt: power(1) ? on, power (0) ? off */
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| }; | |
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| ==== Questions ====
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| # Do we want to expose or hide the block nature of some devces (i.e. force reading multiples of blocksize, or allow reading any number of bytes, with no alignment requirement) ?
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| # How do we connect the dots, such that most of the details can be handled transparently ?
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| # How simple or complex do we want the API to be such that it can work in any stage (including bootblock, assuming some SRAM and a stack are available) ?
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| # Can we integrate this into '''libpayload''' such that the same sources can be used for both coreboot and libpayload ?
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| #* think "Device specfic storage drivers -> [*] Allwinner A10 MMC driver" in '''libpayload''' config
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| # More questions coming soon (TM)
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| == Extending CBFS to support partitioning ==
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| === Reasoning ===
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| * To separate write-protected (RO) and writeable (RW) regions of flash chip
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| * To incorporate relevant FMAP features directly into CBFS
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| * To be able to better handle the requirements of ChromeOS
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| | |
| === Tentative terminology ===
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| * Partition
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| ** A region indexed by CBFS
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| * File
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| ** Same meaning as before. A CBFS file that resides entirely within the boundaries of one partition.
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| === Design constraints ===
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| * Backwards compatibility
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| ** New CBFS structure should be backwards compatible with old structure
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| ** Old payloads should still be able to access old features of CBFS
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| === Tentative API ===
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| * cbfs_get_file(const char *name) <- Get file in main partition, also backwards compatible
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| * cbfs_get_partition(const char *name) <- Get location of partition other than main (or even main)
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| * cbfs_get_partition_file(cbfs_part_t partition, const char *name) <- Get file in given partition
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| === Hypothetical examples ===
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| ==== Partition in read-write portion of flash ====
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| Here, we assume that "rw1" is not in a write-protected area of flash.
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| void *rw1 = cbfs_get_partition("rw1");
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| file *romstage cbfs_get_partition_file(rw1, "fallback/romstage);
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| load_and_run_stage(romstage);
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| ==== MRC cache ====
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| void *mrc_cache = cbfs_get_partition("mrc.cache");
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| /* Access raw partition, there is no file in this partition */
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| mrc_cache_check(mrc_cache);
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| mrc_cache_write(mrc_cache, data);
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