[GSoC 2018: SDHCI MMC Driver]: Week #1 and #2

Blog post by krish_iyer on Sun, 2018-05-06 17:58

Hey folks! here’s the updates of past two weeks on the project!

I have cloned the latest haiku source and built the image file. With the generated image file I have emulated sdhci-pci device successfully. Following are the instructions to be followed:

Cloning the source code

git clone https://github.com/haiku/haiku.git
git clone https://github.com/haiku/buildtools.git

Compiling Source Code

Create a directory where you are going to save the build image and related files

mkdir generated.x86_64; cd generated.x86_64

For compiling

../configure --cross-tools-source ../../buildtools --build-cross-tools x86_64

Building Image

Before building the image you need to install some dependencies

sudo apt-get install git nasm autoconf automake texinfo flex bison gawk build-essential unzip wget zip less zlib1g-dev libcurl4-openssl-dev genisoimage libtool

For creating nightly anyboot Haiku iso image

jam -q -j2 @nightly-anyboot

Error! while building

Now if you getting an error while building, specifically about haiku revision. Then,

cd haiku/build/jam
cat UserBuildConfig

Now copy hrexxxxx, and change directory to haiku/generated.x86_64/build

cd haiku/generated.x86_64/build

Then create and write into the file

echo -n "hrevxxxxx" > haiku-revision

After the building and emulation of the device, I have started finding out the device on the PCI bus so that I can add functionalities for data transfer and many more.

Emulation with Qemu

Installing Qemu

apt-get install qemu

Boot OS in Virtual Drive

First of all create a virtual harddrive in which you are going to boot the OS

qemu-img create haiku-vm.img 10G

Now boot the OS in virtual drive

sudo qemu-system-x86_64 -boot d -cdrom haiku/generated.x86_64/haiku-nightly-anyboot.iso -m 512 -hda haiku-vm.img

Now you can simply run the virtual drive

sudo qemu-system-x86_64 haiku-vm.img


For emulation a sdhci-pci device

qemu-img create sd-card.img 10G
qemu-system-x86_64 haiku-vm.img  -drive if=sd,index=0,file=sd-card.img,id=mydrive -device sdhci-pci 

Creating Device Driver

I have referred device manager doc as it mentions following things:

  • The object device_node describes the functionality and also specification of the device device_node has modules and attributes. The node must have a module and other components are optional.
  • When the system starts only a root node gets registered. The root node has hardware bus like PCI. root node( PCI bus)-> parent node(devices on PCI bus)-> child node(specific to device and attach functionalities specific to device)
  • Whenever a device is attached to PCI bus, it registers a child node for each device on the bus For exploring the hardware in the computer, the system has device drivers.
  • Now according to the system commands, the system will scan for the driver that provides that functionality.

APIs implemented so far:

  • supports_device(): It actually checks if the device belongs to PCI bus and filter out for sdhci-pci device out of all the devices on the pci bus.
  • init_device(): it creates a private data structure(device_cookie) for uninit_driver(), register_child_devices(), rescan_child_devices(), device_removed(), suspend() and resume().

To make the driver module loadable:

  • Module name must end with driver_v1(SDHCI_PCI_DEVICE_MODULE_NAME “busses/mmc/sdhci_pci/driver/v1”)

  • Declaring module dependancy array(module_dependency module_dependencies[] = { { B_DEVICE_MANAGER_MODULE_NAME, (module_info**)&gDeviceManager }, {}};)

  • Declaring structure for driver module info

Loading the module

jam -q sdhci_pci

will create a binary in


You have to place it in


After rebooting you can check debug messages in

cat /var/log/syslog | grep sdhci_pci

Now I am working on finding out number of slots and registering them as child devices with their base adresses.
I have been updating the code on my remote github repo[1] almost everyday, feel free to review it :). Thanks!