Thursday, March 4, 2010

iPhonelinux Wishlist

Planetbeing's words from the iphonelinux github:
"This is just my personal WISHLIST. You might have different priorities. If you want to help, just submit patches that you think are helpful. If you need ideas, just refer to this list. Take it off the list in your patch when you finish something off the list. I'll try to give as much help and guidance as I have time to (which may not be much). 
This is not an exhaustive list, but just stuff I think people can actually deliver on reasonable timescales. For example, notice the conspicuous absence of "figure out how to make phone calls". It's roughly divided based on skillset.  
Jobs for C coders that may not have much RE or driver experience:  
1. Simplify driver code: An early goal of this project is to remain faithful to how the iPhone firmware operates the hardware. Some of it does not actually make sense or is otherwise not very efficient. We have a better understanding of the hardware now and can afford to write better drivers with that understanding. This is essentially refactoring.  
2. Refactor openiboot: I'm not sure I like the way openiboot is laid out right now. There's got to be a neater way to organize this. I'd like something that has less messy defines and a more consistent style so it's easier to read, perhaps individual folders for each module, and the ability to easily include or not include any individual module. An emphasis should be put on ease of porting. 
3. Add multitasking: A great project for students in or just out of OS classes. I've been too lazy to add true multithreading primitives: mutexes, semaphores, condition variables, and also multitasking in general. A lot of stuff is run in interrupt contexes or interrupt-disabled contexes. Writing drivers requiring blocking I/O is a pain. It's time for a true multitasking kernel. Should be done in coordination with #2.  
4. Write a gdb stub for openiboot: Those things are tiny and it shouldn't be that bad. Just have it communicate over the existing USB driver now. We wouldn't be able to debug interrupt contexts for now, but it's better than nothing.  
5. Someone needs to MAINTAIN the build script for the toolchain. Or else figure out if/how we can just build everything using Apple's or the community's iPhone OS toolchain. I'm pretty sure we can. It's not like we use the elf wrapper currently.  
6. It might be cool to be able to parse the iPhone's own device tree for some of base addresses. Might make porting less of a pain.  
7. With help from CPICH, we've determined the vibrator and speaker controls are in the baseband, both controlled through the at+xdrv command. Knowing this, the next step is to make sure we can talk to the baseband through the UARTs. This shouldn't be that bad since iBoot used to do it, and we already have UART code.  
8. I've implemented the firmware upload part of Libertas WLAN driver for Marvell 8686 to test out the SDIO functionality. It appears to work. Therefore, we have validated readb, writeb and writesb. More of it should be implemented to validate SDIO device interrupt handling and also readsb. After that, we will definitely have enough to support working wi-fi in the Linux kernel!  
Jobs for people who want to get their hands dirty with drivers:  
1. Look at TheSeven's NAND FTL code in Rockbox and CPICH's reverse engineering efforts to figure out the FTL write code and get it working.  
2. Write a new USB driver: I hate the current one. TheSeven might have some better code.  
3. Can we steal some code from that userland bluetooth stack and put it on top of our UART code? It might be even cleaner than USB, ironically, since we can probably do it all without interrupts.  
Jobs for reverse engineers:  
1. Port openiboot to unsupported platforms like ipt2g, ipt3g and iPhone 3GS.  
 2. For some reason, the NAND chips stop working after the iPhone is on for a long time. They're fine after a reboot. Figure out why that's happening.  
3. Get multitouch working for Zephyr2. It's a subclass of the Zephyr1 that I investigated, and at least some functions are shared, so it shouldn't be terrible.  
4. Figure out how to talk to the light sensor. It's a TSL2561 according to the ioreg. The slave address is 0x92/0x93 according to the ioreg "reg" setting and is one of the slave addresses allowed on the TSL2561. It's on i2c0 according to ioreg. It all looks good except for the fact I cannot get a response out of this part. I even bruteforced all the slave addresses on i2c0 and only got responses from the PMU, the accelerometer and the Wolfson, stuff we already know how to talk to. What's going on? Is it just my 2G is broken?  
5. Figure out the new FTL they're using on the newer devices. That's going to be a pain.  
Thanks for reading all this. I'm impressed."