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 RFC for the chip specification architecture \begin{abstract} At the end of this document is the original message that motivated the change. \end{abstract} \section{Scope} This document defines how LinuxBIOS programmers can specify chips that are used, specified, and initalized. The current scope is for superio chips, but the architecture should allow for specification of other chips such as southbridges. Multiple chips of same or different type are supported. \section{Goals} The goals of the new chip architecture are these: \begin{itemize} \item seperate implementation details from specification in the Config file (translation: no more C code in Config files) \item make the specification easier for people to use and understand \item remove private details of a given chip to the chip file as much as possible \item allow unique register-set-specifiers for each chip \end{itemize} \section{Specification in the Config file} The specification looks like this: \begin{verbatim} chip [path=] [""] \end{verbatim} The name is in the standard LinuxBIOS form of type/vendor/name, e.g. "southbridge/intel/piix4e" or "superio/ite/it8671f". The class of the chip is derived from the first pathname component of the name, and the chip configuration is derived from the following components. The path defines the access mechanism to the chip. It is optional. If present, it overrides the default path to the chip. The configuration defines chip-specific configuration details, and is also optional. Note that an empty configuration will leave the chip with no enabled resources. This may be desirable in some cases. \section{Results of specifying a chip} When one or more chips are specified, the data about the chips is saved until the entire file is parsed. At this point, the config tool creates a file in the build directory called chip.c This file contains a common struct containing information about each individual chip and an array of pointers to these structures. For each chip, there are two structures. The structures contain control information for the chip, and register initialization information. The names of the structures are derived by flattening'' the chip name, as in the current linuxbios. For example, superio/ite/xyz uses two structs, one called superio_ite_xyz_control and one called superio_ite_xyz_init. The control struct is initialized from the chip name and path information, and has a pointer to the config struct. The config struct is initialized from the quote string \begin{verbatim} From rminnich@lanl.gov Fri May 16 10:34:13 2003 Date: Tue, 13 May 2003 08:11:46 -0600 (MDT) From: ron minnich To: linuxbios@clustermatic.org Subject: RFC:new superio proposal Abstract: The superio architecture for linuxbios has worked for the last 2 years but is being stretched to the limit by the changes in superio chips. The architecture depended on superio resources being relatively constant between chips, but this assumption no longer holds. In this document we propose several alternatives and solicit comments. Overview: The superio architecture in linuxbios was developed over time, and modified as circumstances required. In the beginning it was relatively simple and assumed only one superio per mainboard. The latest version allows an arbitrary number of superios per mainboard, and allows complete specification of the superio base I/O address along with the specification of reasonable default valures for both the base I/O address and the superio parameters such as serial enable, baud rate, and so on. Specification of superio control parameters is done by a configuration line such as: nsuperio sis/950 com1={1} floppy=1 lpt=1 This fragment sets the superio type to sis/950; sets com1, floppy, and lpt to enabled; and leaves the defaults to com1 (baud rate, etc.) to the default values. While it is not obvious, these configuration parameters are fragments of a C initializer. The initializers are used to build a statically initialized structure of this type: struct superio { struct superio_control *super; // the ops for the device. unsigned int port; // if non-zero, overrides the default port // com ports. This is not done as an array (yet). // We think it's easier to set up from python if it is not an // array. struct com_ports com1, com2, com3, com4; // DMA, if it exists. struct lpt_ports lpt1, lpt2; /* flags for each device type. Unsigned int. */ // low order bit ALWAYS means enable. Next bit means to enable // LPT is in transition, so we leave this here for the moment. // The winbond chips really stretched the way this works. // so many functions! unsigned int ide, floppy, lpt; unsigned int keyboard, cir, game; unsigned int gpio1, gpio2, gpio3; unsigned int acpi,hwmonitor; }; These structures are, in turn, created and statically initialized by a config-tool-generated structure that defines all the superios. This file is called nsuperio.c, is created for each mainboard you build, only appears in the build directory, and looks like this: === extern struct superio_control superio_winbond_w83627hf_control; struct superio superio_winbond_w83627hf= { &superio_winbond_w83627hf_control, .com1={1}, .com2={1}, .floppy=1, .lpt=1, .keyboard=1, .hwmonitor=1}; struct superio *all_superio[] = {&superio_winbond_w83627hf, }; unsigned long nsuperio = 1; === This example shows a board with one superio (nsuperio). The superio consists of a winbond w83627hf, with com1, com2, floppy, lpt, keyboard, and hwmonitor enabled. Note that this structure also allows for over-riding the default superio base, although that capability is rarely used. The control structure is used to define how to access the superio for purposes of control. It looks like this: === struct superio_control { void (*pre_pci_init)(struct superio *s); void (*init)(struct superio *s); void (*finishup)(struct superio *s); unsigned int defaultport; /* the defaultport. Can be overridden * by commands in config */ // This is the print name for debugging char *name; }; === There are three methods for stages of hardwaremain. First is pre_pci_init (for chips like the acer southbridge that require you to enable some resources BEFORE pci scan); init, called during the 'middle' phase of hardwaremain; and finishup, called before the payload is loaded. This approach was inspired by and borrows heavily on the Plan 9 kernel configuration tools. The problem: When the first version of the superio structure came out it was much smaller. It has grown and in the limit this structure is the union of all possibly superio chips. Obviously, in the long term, this is not practical: we can not anticipate all possible superio chips for all time. The common PC BIOS solution to this type of problem is to continue with binary structures but add version numbers to them, so that all code that uses a given structure has to check the version number. Personally, I find this grotesque and would rather not work this way. Using textual strings for configuration is something I find far more attractive. Plan 9 has shown that this approach has no real limits and suffices for configuration tasks. The Linux kernel does more limited use of strings for configuration, but still depends on them. Strings are easier to read and work with than binary structures, and more important, a lot easier to deal with when things start going wrong. The proposed solution: What follows are three possible ideas for specifying superio resources and their settings. A common part of the new idea is to eliminate the common superio structure, due to the many variations in chips, and make it invisible outside a given superio source file -- the superio structure is now private to a given superio. Thus, sis/950/superio.c would contain its own superio structure definitions, and also might contain more than once instance of these structures (consider a board with 2 sis 950 chips). The control structure would change as follows: struct superio_control { int (*create)(struct superio *s); void (*pre_pci_init)(struct superio *s); void (*init)(struct superio *s); void (*finishup)(struct superio *s); unsigned int defaultport; /* the defaultport. Can be overridden * by commands in config */ // This is the print name for debugging char *name; }; I.e. we add a new function for creating the superio. Communication of superio settings from linuxbios to the superio would be via textual strings. The superio structure becomes this: struct superio { struct superio_control *super; // the ops for the device. unsigned int port; // if non-zero, overrides the default port struct configuration *config; }; So now the question becomes, what is the configuration structure? There are several choices. The simplest, from my point of view, are keyword-value pairs: struct configuration { const char *keyword; const char *value; }; These get filled in by the config tool as before. The linuxbios libary can then provide a generic parsing function for the superios to use. The remaining question is how should the superio command look in freebios2? superio sis/950 "com1=115200,8n1 lpt=1 com2=9600" or superio sis/950 "com1baud=115200 lpt=1 com1chars=8n1" or superio sis/950 ((com1 115200 8n1) (lpt 1)) So, my questions: 1. Does this new scheme look workable. If not, what needs to change? 2. What should the 'struct configuration' be? does keyword/value work? 3. what should the superio command look like? Comments welcome. I'd like to adopt this "RFC" approach for freebios2 as much as we can. There was a lot of give-and-take in the early days of linuxbios about structure and it proved useful. There's a lot that will start happening in freebios2 now, and we need to try to make sure it will work for everyone. Those of you who are doing mainboards, please look at freebios2 and see how it looks for you. There's a lot of good work that has been done (not by me so far, thanks Eric and Stefan), and more that needs to be done. Consider trying out romcc as an "assembly code killer". See how it fits together and if you can work with it or need changes. Bring comments back to this list. thanks ron \end{verbatim}