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11da3403e9
For nearly all commands in U-Boot the '?' variable is handled the same way with 0 meaning success, 1 meaning any failure. Explain this in the general rules section of the cmdline documentation (with a link to a counter example) and then remove the redundant wording from most commands. We retain a section about the return value in a number of places where we are doing something such as always returning a specific value or we have useful additional information to go along with the normal return codes. Signed-off-by: Tom Rini <trini@konsulko.com> Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
64 lines
1.1 KiB
ReStructuredText
64 lines
1.1 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0+
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.. index::
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single: cpuid (command)
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cpuid command
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=============
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Synopsis
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--------
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::
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cpuid <op>
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Description
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-----------
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The cpuid command requests CPU-identification information on x86 CPUs. The
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operation <op> selects what information is returned. Up to four 32-bit registers
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can be update (eax-edx) depending on the operation.
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Configuration
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-------------
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The cpuid command is only available on x86.
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Example
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-------
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::
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=> cpuid 1
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eax 00060fb1
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ebx 00040800
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ecx 80002001
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edx 178bfbfd
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This shows checking for 64-bit 'long' mode::
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=> cpuid 80000000
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eax 8000000a
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ebx 68747541
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ecx 444d4163
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edx 69746e65
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=> cpuid 80000001
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eax 00060fb1
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ebx 00000000
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ecx 00000007
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edx 2193fbfd # Bit 29 is set in edx, so long mode is available
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On a 32-bit-only CPU::
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=> cpuid 80000000
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eax 80000004
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ebx 756e6547
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ecx 6c65746e
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edx 49656e69
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=> cpuid 80000001
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eax 00000663
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ebx 00000000
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ecx 00000000
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edx 00000000 # Bit 29 is not set in edx, so long mode is not available
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