configtxt/boot: Update arm_64bit flag #3903
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A casual reader might have previously assumed Raspberry Pi 5 requires this flag to boot in 64-bit mode. That is incorrect - Raspberry Pi 5 follows Raspberry Pi 4 in assuming 64-bit mode by default. Edit the defaults line to reflect this, and further edit it to include more complete platform names.
| @@ -29,7 +29,7 @@ If set to 1, the kernel will be started in 64-bit mode. Setting to 0 selects 32- | |||
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| In 64-bit mode, the firmware will choose an appropriate kernel (e.g. `kernel8.img`), unless there is an explicit `kernel` option defined, in which case that is used instead. | |||
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| Defaults to 1 on Pi 4s (Pi 4B, Pi 400, CM4 and CM4S), and 0 on all other platforms. However, if the name given in an explicit `kernel` option matches one of the known kernels then `arm_64bit` will be set accordingly. | |||
| Defaults to 1 on Raspberry Pi 4, 5, 400 and Compute Module 4, 4S platforms. Defaults to 0 on all other platforms. However, if the name given in an explicit `kernel` option matches one of the known kernels then `arm_64bit` will be set accordingly. | |||
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I'd add CM5 as well - everyone knows its coming.
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I try to avoid mentioning any potential products ahead of a formal announcement, especially if I've structured the text such that any new products could be trivially included in the line.
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Agree with Tom in principle. But for my own edification: I assumed that CM5 wouldn't support 32-bit mode at all, just like Pi 5. So I don't think we need to add it here at release. Is that correct, @JamesH65 ? Or will CM5 support 32-bit mode?
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I believe it's actually the SoC (and not the specific Model) that determines if it's capable of booting 32-bit kernel only (BCM2835, BCM2836), either 32- or 64-bit kernel (BCM2837, RP3A0, BCM2711), or 64-bit kernel only (BCM2712) ?
But (in general) we explicitly list the Models in documentation rather than SoCs, because people find it easier to identify their Model than to identify their SoC 🧦 😉
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The NOTE block underneath this text also says "Raspberry Pi 5 only supports a 64-bit kernel, so this parameter has been removed for that device." |
A fair note. I'm not sure the best way to handle this, then - I'm fairly certain I don't like the disjointed-mentions around this flag, but perhaps it would be better served by trimming 5 from this change, and moving the note block above this paragraph? |
Might be worth splitting the Pi 5 info out of the current long NOTE block, and adding it as a separate NOTE block which appears earlier? 🤔 |
The Raspberry Pi 5 does not support the arm_64bit flag at all - and so users should be made aware that if they are reading the documentation in the context of Raspberry Pi 5 they are safe to skip the entire section.
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The latest commit reflects my interpretation of @lurch's suggestion, but I've not seen prior evidence of NOTE blocks being at the start of the config item. |
Accepted. Co-authored-by: nate contino <[email protected]>
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Thanks for the suggestion, @nathan-contino! |
Accepted. Co-authored-by: nate contino <[email protected]>
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LGTM! Thanks for waiting a bit on this. I knew there was a better way to present the info, but I had to chew on it for a little while. I think we're in a much better place now with this change.
Now, to propagate these ideas into the other config.txt entries 😉
| * uncompressed image files | ||
| * gzip archives of an image |
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I wonder if we should remove the plural from these two lines, given that you'll only ever be using one kernel at any given time? And IMHO "archive" usually implies that there's more than one file inside the archive, so perhaps this could be simplified too? (so "uncompressed image file" and "gzip-compressed image file" ?)
A casual reader might have previously assumed Raspberry Pi 5 requires this flag to boot in 64-bit mode. That is incorrect - Raspberry Pi 5 follows Raspberry Pi 4 in assuming 64-bit mode by default.
Edit the defaults line to reflect this, and further edit it to include more complete platform names.