Re: 转发: 回复: About Kernel limitation HCI_MAX_FRAME_SIZE (1024 + 4)

["Chris Lu (陸稚泓)" <Chris.Lu@mediatek.com>]

On Wed, 2026-05-20 at 15:03 +0800, yjg0107 wrote:

Hi Luiz,

I received a question about the restrictions of HCI_CHANNEL_USER and
HCI_MAX_FRAME_SIZE. Since this involves changes related to Kernel HCI
layer, what's your view on relaxing HCI_MAX_FRAME_SIZE limit?

I saw that there was some discussion about this on bluez github, but it
seems there hasn't been any activity for a while. Would you suggest
they directly upload a patch they want and continue the discussion with
you?

> 
> ---------- 转发的邮件 ----------
> 发件人：yjg0107 <yjg0107@163.com>
> 日期：2026年5月7日 17:55
> 主题：回复: About Kernel limitation HCI_MAX_FRAME_SIZE (1024 + 4)
> 收件人："luiz.dentz" <luiz.dentz@gmail.com>
> 抄送：linux-bluetooth <linux-bluetooth@vger.kernel.org>
> 
> 
> 
> 
> 
> 
> 
> 
> Hi Vudentz,
> 
> In the future, BT SIG will introduce the High Data Throughput (HDT),
> which may require transmit larger data size, not just 1024.
> So what's your opinions? Could kernel remove the limitation that
> HCI_CHANNEL_USER can not change MTU?
> Looking forward to your reply, thank you very much.
> 
> B.R.
> Jigong Yin(殷吉功)
> ---------- 回复的原邮件 ----------
> 发件人：yjg0107 <yjg0107@163.com>
> 日期：2026年4月27日 14:40
> 主题：About Kernel limitation HCI_MAX_FRAME_SIZE (1024 + 4)
> 收件人："luiz.dentz" <luiz.dentz@gmail.com>
> 抄送：linux-bluetooth <linux-bluetooth@vger.kernel.org>
> 
> 
> 
> 
> 
> 
> 
> 
> Hi Luiz,
> 
> Question is same as https://github.com/bluez/bluez/issues/2073.
> About Kernel limitation HCI_MAX_FRAME_SIZE (1024 + 4), you said that
> this will be fixed to enable user space changed, from #201 (comment).
> The patch commit is torvalds/linux@09572fc, right?
> 
> However, why HCI_CHANNEL_USER type can not change MTU value? Google
> bluetooth aidl uses HCI_CHANNEL_USER type
> fromhttps://cs.android.com/android/platform/superproject/+/android-la
> test-
> release:hardware/interfaces/bluetooth/aidl/default/net_bluetooth_mgmt
> .cpp line 282.
> 
> Could kernel remove the limitation that HCI_CHANNEL_USER can not
> change MTU?
> 
> Thanks.
> B.R.
> Jigong Yin
> 
> 
> 
> 发自vivo电子邮件
> 
> 

Best Regards,
Chris Lu