genode/repos/os/src/drivers/ahci
Norman Feske bbe3ee8dc5 block_session: server-defined payload alignment
This patch replaces the formerly fixed 2 KiB data alignment within the
packet-stream buffer by a server-defined alignment. This has two
benefits.

First, when using block servers that provide small block sizes like 512
bytes, we avoid fragmenting the packet-stream buffer, which occurs when
aligning 512-byte requests at 2 KiB boundaries. This reduces meta data
costs for the packet-stream allocator and also allows fitting more
requests into the buffer.

Second, block drivers with alignment constraints dictated by the
hardware can now pass those constraints to the client, thereby easing
the use of zero-copy DMA directly into the packet stream.

The alignment is determined by the Block::Session_client at construction
time and applied by the Block::Session_client::alloc_packet method.
Block-session clients should always use this method, not the 'alloc_packet'
method of the packet stream (tx source) directly. The latter merely
applies a default alignment of 2 KiB.

At the server side, the alignment is automatically checked by
block/component.h (old API) and block/request_stream.h (new API).

Issue #3274
2019-05-03 13:53:12 +02:00
..
spec Add missing override annotations 2019-02-19 11:12:11 +01:00
ahci.cc Add missing override annotations 2019-02-19 11:12:11 +01:00
ahci.h block session: remove Block::Session::Operations 2019-05-03 13:53:12 +02:00
ata_driver.h block_session: server-defined payload alignment 2019-05-03 13:53:12 +02:00
atapi_driver.h block_session: server-defined payload alignment 2019-05-03 13:53:12 +02:00
main.cc Add missing override annotations 2019-02-19 11:12:11 +01:00
README default ahci_drv and part_blk Block sessions to read-only 2017-08-28 16:49:51 +02:00
target.mk ahci: transition to the new base API 2016-06-28 11:08:13 +02:00

This directory contains the implementation of Genode's AHCI driver

Behavior
--------

The driver supports x86 32/64 bit platforms and the Exynos5 SOC. If
more than one AHCI controller is present, the first one will be used.
Each active device on each AHCI port will be represented by a Genode
block session. The server must be configured via a policy, that states
which client can access a certain device:


!<start name="ahci">
!  <binary name="ahci_drv" />
!  <resource name="RAM" quantum="10M" />
!  <provides><service name="Block" /></provides> }
!  <route>
!    <any-service> <parent /> <any-child /> </any-service>
!  </route>
!  <config atapi="no">
!    <!-- use model and serial number -->
!    <policy label_prefix="test-ahci" model="QEMU HARDDISK" serial="QM00005" writeable="yes" />
!    <!-- use controller port number -->
!    <policy label_prefix="bench" device="1" writeable="yes" />
!    <!-- read-only access -->
!    <policy label_prefix="boot_fs" device="2"/>
!  </config>
!</start>

In the example above, a session request labeled with "test-ahci" gains access to
a device with certain model and serial numbers, "bench" gains access to
device at port 1, and finally the session "boot_fs" gains read-only access to
port 2. ATAPI support is by default disabled and can be enabled by
setting the config attribute "atapi" to "yes".

ahci_drv supports reporting of active ports, which can be enabled via
configuration sub-node like follows.

!<report ports="yes"/>

The report structure is depicted by the following example.

! <ports>
!   <port num="0" type="ATA" block_count="32768" block_size="512"
!     model="QEMU HARDDISK" serial="QM00005"/>
!   <port num="1" type="ATAPI"/>
!   <port num="2" type="ATA" block_count="32768" block_size="512"
!     model="QEMU HARDDISK" serial="QM00009"/>
! </ports>